I still find that assertion strange. I played 1e before 2e came out, and I adopted 2e right away (I'm pretty sure that I bought 2e on day of release). Now, I haven't played either system since then (I have always moved forward with editions without looking back) but I honestly don't remember 2e being remotely backwards compatible. Maybe I was too young at the time to understand how to kit-bash or reverse-engineer stuff to fit them together, but no one I knew ever allowed any 1e feature in their 2e games.
I've head the assertion a few times here, so I have to assume that we were wrong at the time and the editions were closer than they appeared.