No. The majority don't. And they don't care. For them, faith in the doctrine is more important and desirable than understanding the doctrine itself.
This has certainly been my experience as well. For context, I have never been a JW myself but rather am a person who has been trying to get a loved one out. One of the very first things I discovered in the midst of all my research, is that he doesn't fully know or understand what the heck he believes but "believes" it anyway! This is indeed extremely frustrating and almost impossible to debate or reason against. I have found over and over again that before we can discuss how or why a particular point is questionable, I first have to explain to him WHAT IT IS THAT HE "BELIEVES" and *then* attempt to explain why it is questionable -- how screwed up is that?? Plus it doesn't do a whit of good anyway, I mean a person who basically admits "I don't really understand what the teaching is but whatever it is I believe it" well yeah. I gave up on logical debate long ago. The YouTube responses you describe sound painfully familiar to me; at least with my own JW, I would say that he genuinely believes the parroted response is a valid response and thinks no further beyond that, end of discussion. It is maddening :-(