PTR not only doesn't record %100 of
hands played, but didn't start recording hands up until like a year or two ago. In other words, what you see on PTR isn't the history of
online poker. It's the history of the last couple years.
Another thing is that PTR doesn't always know all the screennames of a certain player. Not everyone plays all their volume on one screen name on one site.
That said, someone like baluga whale has both run bad for a good ~year (?) and subsequently taken a break from poker, but is a fantastic coach. One of the best, actually.
tl;dr: don't read into PTR too deep. That said, don't just get any no-name coach either; any good coach will happily supply a graph of his past 200k hands or past year or whatever from HEM/PT3 to potential students.