I do agree with you as to why the heck in 2021 they couldn’t release 5.1 as LPCM/D-THD/DTS HD MA etc, ad nauseum on a blu ray...why they chose lossy dts on a dvd??? Bizarre. And unless Esoteric doesn’t have blu ray authoring abilities and equipment...
As has been discussed before, it's a budget issue. Blu-Rays are much more expensive to author/manufacture than DVDs. @edisonbaggins' excellent interview with Bruce Soord last year touched on this.