Any historical connection between 筵席 and 宴席?
In my opinion, there are no similar origins or any historical connections between these two words.


宴 means 宴请 here. It's a verb. And the word 宴席 is also a modern Chinese word widely used in our daily life.
筵 means 竹席. You can find it's composed with 竹 on top, so apparently it is a noun. 筵席 is more or less too formal and ancient for daily use. I will never use it except the old saying 天下没有不散的筵席.


Your analysis is also reasonable. It seems just a coincidence.