The presence of these 4 titles does make sense, they did the complete first batch.
Just wonder why these 5.1 masters are sitting somewhere without a release. The EJ sacd had a good sale everywhere.
Well, there are a number of albums that were mixed to 4.0 Quad in the '70s or 5.1 Surround more recently that haven't seen the light of day.
I like the earlier suggestion about contacting Chad Kassem about a potential release. A very interesting idea !