I’m about to go through a load of my old X-Trans files soon so I’ll be looking at this closer now when I do
Admittedly I have nothing to compare against as I am only using PL9 now (can no longer access my last version PL5) but recent exports of two test files (XT-4 with 55-200) I dug out whilst evaluating PL9 were both perfectly sharp (one of a Jay the other a Squirrel) to my eyes and gave no reason to complain.
Maybe they would have been better under PL7 though hence your findings.
Anyway. I don’t know if you look in the PureRaw section on here but prior to going with PL again I toyed with getting PR and sticking with LR. In the end I never trialled PR but I wonder if it’s related to the experience/findings some are seeing and the ‘work arounds’ they have employed may help.
Worth a look if you haven’t seen it already.