@leo It's not cross-signing; those entries with identical signatures are signed by the same key (here, the one of the NewPipe team & signed by them, so same APK).
For NewPipe, I'd recommend installing it from their repo, for faster updates (YT breaks its own stuff frequently, in effect breaking the app; their own repo is where the adjusted APK will show up first; F-Droid's repo usually takes 2..5 days longer; IzzyOnDroid just a few hours, so that would be fine as well, depending on your needs).