To me Pro refers to getting paid opposed to skill, all else is amateur...as in college vs pro sports..
Yep, there are lots of "amateur" arranger players out there with
advanced playing skills that surpass many so called "pros".
Many of my clients are absolutely outstanding players, but earn
no money from it...they play at home
for their own enjoyment.
Just because you get paid, doesn't mean that you are an
advanced player, although,
by definition you are considered a "professional".
Ian