I've found that some very well read people assume others have their vocabulary or knowledge. Seen that as well with people that think some of us are just writing things everyone has heard.

Some overestimate their knowledge, others underestimate it. In my experience there are always people on both sides of us. Those that know more and those that know less. This applies to the younger and older but also isn't dependent on age.

And many of us have read/heard so much we forgot things.