Actually i have always found it quite annoying to not be able to take screenshots in private tabs ( in firefox). So this sounds like an improvement. Or am i missing something?
Per the note below, having done some digging this was definitely an intended change, however I also have a work around...
Source:
https://chromium-review.googlesource.com/c/chromium/src/+/4135877
Workaround:
1. Open Chrome Flags - chrome://flags/
2. Set the following -
Discussion
If you're happy to be able to screenshot incognito tabs then the current upstream chromium implementation, and Vanadiums default going forward is fine for you.
If you wish to protect them again as was the case until this change then the above is required.