Earlier quoted context omitted.
Maybe. I think Feynman had a point. From my experience “experts” who are unable to explain well typically have an incomplete understanding. Language and knowledge are linked to a degree. Personally I have had subject I thought I was an expert an and when I went to explain them I realized the shortcomings of my understanding. Later when I was truly an expert my ability to explain them improved.
My biggest challenge with explaining things to people is the stuff they already know that's either wrong or not relevant. To save the effort of finding out later, I now ask people to explain it to me first, tell me everything they know about this, before I can figure out how far back I have to step before explaining it all.
Look at the ABC Conjecture catastrophe.