100%. I recently took a pdf map from a foreign country, rotated it, and. overlaid English notes using macOS preview. I saved and it opened fine in Preview. But when I tried opening the edited map pdf on iOS in the native pdf viewer it was not rotated so the notes were meaningless. Acrobat Reader for iOS opened it correctly.

So ya looking at binary size alone is not useful. Acrobat may be bloated but there also seems to be some robust code there covering edge cases other readers mess up.