Ok, a few notes: i had already noted that after upgrading to 8.2.2, the pivot grid looked horrible. I didn't have time to look into it. Then this issue cropped up. I spent a long time going through (the horribly slow) SC, filtering for xaf posts with "pivot" in the post, looking for clues. I stumbled across "BugReport Details: XAF 8.2, Web, action buttons in detail view are different sizes, too high and look messy". This solved both my messy web buttons, AND the pivot issue, believe it or not.
So, the new thrust of this thread: why wouldn't the ProjectConverter take into account this most basic of issues? Don't just upgrade references, but other support files of which CSS obviously plays a significant role. thanks for listening, drew..
ps: it is remarkable how stress levels fall when problems seemingly outside of your control disappear.