Physics students generally not understanding physics isn't an isolated case. The point is that the majority of people don't really 'understand' the concepts that they talk about a lot of the time. What does it even mean to understand something? Is it binary? Is it a continuous scale?

There's no test for 'true' understanding, there's no test for awareness. There's fundamentally no way to distinguish a p-zombie from a conscious being. It's possible that p-zombies are also fundamentally incapable of distinguishing themselves from 'truly' aware beings, in which case the distinction between awareness and non-awareness is meaningless.

Trying to detect 'awareness' or 'understanding' in communications is a dead end. There is no reason to believe that a human doesn't also 'just 'regurgitate smooth language fragments because that's what it was trained on'. In fact, I see a lot of that in the professional services world. People have built entire careers by stringing plausible-sounding sentences together even though they're completely devoid of meaning if you actually try to parse them. The most interesting thing is that those people genuinely believe that they know what they're talking about. They rarely admit or believe that they lack understanding, even if it's clear to everyone around them.