Found this gem tonight on Ligonier:
It has often been remarked that Paul clearly implied that he spent three years being taught by Jesus Himself (Galatians 1:12)
, either directly or (perhaps more likely) through the study of the Word. Thus, like the other apostles, Paul studied with Christ for three years before beginning his ministry (compare Acts 1:21).
Emphasis mine.
I had never noticed that before!