I think the initial confusion is that you mean rotj 2.5* (not 2.7) is still listed.
And I think that’s a valid question (which might have a good answer/justification):
Why is rotj 2.5 still listed when rotj 3.1 is released (and presumably supercedes it)?Exactly my point. I wonder if it’s because ROTJ 2.5 is made like all the others DEED (by adding different sources together), whereas 3.0 and 3.1 are from a 1983 source, and demand a different set of skills.
No, ROTJ 2.5 also used 1983 film scans mixed with the Blu-rays. 3.x uses 1983 films scans mixed with the UHDs. It’s the same general process, just with better-quality sources in 4K. I suspect 2.5 wasn’t removed when 3.0 came out because 3.0 had a major error, and 2.5 was the fallback. Then by the time 3.1 came out, failing to remove it was an oversight.