Or that there are talkie bits which are deeply unconvincing (the kindly prison warden almost immediately converts the hardened gangster to the path of reform by lecturing him briefly) -- but which, I suspect, would probably be much more believable as silent scenes, where (for example) we'd accept that there was a kind of compression going on.

And the fact that when you can't hear the dialogue—or you accept the one title card to stand in place of an entire conversation—your brain can fill in the most persuasive, convincing lecture imaginable and therefore you believe in it, whereas the talkie reality is kind of preachy and not all that smoothly delivered, or whatever the particular problem is. The human brain is so good at filling in narrative ellipses, if your screenwriter is going to take over for it, they had better know what they're doing.