I cannot see anywhere that MDN say the explanation might be wrong.
No need to make things up if you have the sources anyways.
Also hallutination was probably the wrong word to use for LLMs being incorrect since it might imply they could be correct if they would only just focus on the right input data rather than, say, simply not understanding complex technical concents, but I guess that ship has sailed.
The latter would be very different interpretation and some here would probably agree with that accusation