It looks like the discussion has shifted from what I understand the original question to be. And that is, when using (in coherence mode) one window in full screen mode, why the app looks like it re-adjusts its resolution the whole time. The following KB article, which attempts to defend another related issue, shows what changed in PD 9:
http://kb.parallels.com/en/117062. But it shows, all too naively, why we get this jumping.
Bottom line, is that despite complaining in PD 9, and despite feedback as a beta tester in PD10, Parallels have decided to ignore this. I understand their logic, but I believe it to be flawed. It's flawed because of an assumption that most people are running windows in full screen or in a window on a huge monitor. It's also flawed, because Parallels appear to focus on the technical side and not the user experience.
In 2012, three out of every four macs sold as a MacBook (and that surely as increased over time). So, most of us ARE using MacBooks. It's also been proven that most people are running Parallels to be able to run Microsoft Office (in particular Excel, whose Mac version is woefully lacking). So, it makes sense we want to move from a full screen windowed office app in Parallels back to Finder or Apple Mail or Apple Calendar. Or even to a non-full screen Windows Explorer.
But, to do that, we have to suffer the constant re-adjustment of the resolution.
I don't mean to be rude, but I find it almost pathetic that a year later we are still at the same point.
So, to answer the original question: No! It has not changed. I can confirm that the adjustment has sped up over the time of PD9 and PD10 betas. But it's still there, and it's just as annoying.
In v9 if you were in Coherence mode and put one of the windows in full screen, every time you did an cmd-tab back to that window the screen would shift around for a few seconds as if it was getting a new resolution. It was very annoying, and the main reason I rarely use Parallels now. Can someone tell me if this was fixed in v10?