Very LONG rant...
You have to consider the entire production chain for the duplication.
Basically you have these steps, after the creation of a full 8-track master tape for duplication (8TMfD):
1) continuous copy of the 8TMfD at high speed (variable from 10 to 20x due to evolution of the decks) to a large pancake of tape, with the pilot tone at some Hz in order to give a reference point for step 2
2) spooling and division of the pancake into single hubs for a single cartridge, various techniques for that.
3) insertion of a single hub with tape into a single cartridge, bottom part, already assembled with roller and pads (felt or spring)
4) application of sensing foil to close the tape ring and thread the tape into the guides
5) application of the top part of the cartridge and eventual marking (not all duplicators did that) of a serial number, linked in some ways to the catalog number of the release; may be rubber printed or iron-stamped.
6) Special ONLY for some kind of cart:
- RCA, USA, Canada, Italy, partial UK: closing of the cart with the aluminium rivet on the back
- Capitol-USA only, later WEA, JVC, and other Japanese: closing of the cart with a screw in the front
(Blank tapes varies and are not considered here)
- All others kind of cart, original LearJet design later licensed to Ampex, Columbia USA design etc etc etc use a form of snap-in closing for secure the cart, various design used depending on the year and patent used/applied for that specific cart style.
7) label application with thermal glue on the back of the paper label or other methods
8) packaging of the single cart into cardboard sleeve or only with a plastic tape protector, wrapping and packing into boxes for distribution.
Basically all steps are not only linked togheter, of course, but very specific one with the other: a production line of RCA-riveted cart CAN'T USE, unless reorganized on one or more steps, a Columbia snap-in cart, because all the machinery for the following steps are very strict in specs.
A) assembly the bottom part of cart have specific pieces: roller, plastic or rubber, roller size, pads, felt or spring, tape guides (common in early RCA carts) etc etc etc. These steps were automated, so you need a different tailored machine in order to use another cart design which has different specifics;
B) hubs spooling (with the recorded tape) are different between duplicators and have different grip point for the spooling seen in point 2), different sizes, different center holes etc; that's another automated process so it's very specific;
C) steps 3 (partially, later also this was automated) and 4 were done by humans, at least on the videos i've seen and other sources found during the years; don't think the steps 4 has ever been automated, too complicated and precise for a machine in the seventies (splicing tapes, applying sensing foil, running the tape thru the correct path and keep it tense)
D) Step 5 is closely linked to step 6 for the production lines that need a extra bit of thing (rivet or screw) or not; step 6 on Columbia/Ampex/etc duplication cart line is absent.
E) labelling was automated, so you need to have a specific kind of label in one single piece of two depending of the machine used for that; style can vary but is less problematic than the steps above
F) packaging also was automated, so the extact size of the cart was crucial for the whole assembly line to work properly. That's the reason that even when a BIG duplicator changed something on the cart, for example RCA went from the rivet for secure closing of the cart to thermal sealing on the borders, the exact size of the external cart were identical between the earlier and later model, so you won't need to change some producion line steps (bottom assembly, pack&wrap) that was still ok and modify just one (top assembly with the thermal glueing) and remove the unused one (riveting).
All that of course need a specific kind of machines, built-in for the bigger companies or bought from someone who did the things needed for the various steps. Once a BIG company has a proprietary reference-design for one production line of 8-track tapes cartridges it make economical sense to share it with their affiliates or delivering the entire set of machines to another country, or building in another country the same machine with the same parts.
This is why you can find RCA-style riveted carts in USA, Canada, Spain, Italy, part of UK, and some Brazilian too; they had basically the same production line, copied in various places.
For the record, RCA France didn't use the USA production line and RCA France-related titles on riveted carts were duplicated in Italy for export; same situation for RCA Germany. Spain used later the same production line of USA carts, earlier RCA ones have no resemblance with the RCA USA ones; UK too varied but on reverse, and you can see the difference even on quads, that EMI earlier ones were on black riveted carts (RCA style 100%) then switched to another production line. I have no idea IF all UK riveted-carts were done abroad or there was a production line that later RCA UK dismissed or retooled for other cart-specific design OR if the RCA UK production line for riveted carts were moved from UK to Spain (looking at the production years of the tapes on the two countries open this possibility, when UK stops this production line, soon Spain begin).
At the end, if the duplicator was named RCA Canada or Cinram Canada it is relative; what is clear is that the RCA-style production line was implemented and used there, because only THAT production line can work out THAT kind of cart. So, it's RCA in all, or just a rebranding of RCA.