I can only guess at the possible reasons why:
1. There were problems with rev 7 so they stopped making them and rolled back to an older version. I’m sure that chip tower near the trap door added costs that Commodore didn’t want to have to pay…
2. Only certain factories were producing rev 7 while most of the others stayed on older revs.
3. Given how Commodore’s various international marketing divisions had to place orders with HQ, maybe most countries didn’t want rev 7 machines. (Just like how no divisions ordered the finished A2200.) Maybe they didn’t want to have to provide post-sale support/service for another variant.
As to the strange matter of rev 7 being older than expected, another possibility that I wonder about is that rev 6 was an internal version that was never released, like the rev 5 A2000. The next version was 7, they pulled that one from distribution, then created rev 6A, a fork from rev 6 instead of fixing/iterating rev 7.
