Often you need exactly that. Because it's the unique words the machine will get wrong. If you look for machine learning tutorials/presentations that mention a certain algorithm, the name of it must be correctly transcribed. At the moment, it appears to me that 95%+ of words work but exactly the ones that define a video often don't. But then again getting those right is hard, there's not much training data to base it on.
As for the users, sure the translation may not be perfect, but I'm sure if you were deaf had no other way of watching a video, you would be just fine with the current quality of the transcription.