I'd be careful there, private hours do count towards your commercial hours. If you fly 900 private, you have 0 commercial hours. I've got a few friends who work commercially and fly, manage and operate a privately owned aircraft for the owner on the side. While the FOI (in this particular case and this particular FOI) didn't have a problem that the side work was in fact private, he did have an issue when said pilot exceeded 900 flt hrs for that year. He was then in a situation where he was unable to operate privately or commercially.
The very grey area on hours is your duty limitations between private and commercial rest periods. I believe in common sense and discretion others believe that if its legal (even if its grey) then its open to manipulation.
PS. As for the anecdote: I don't particularly care if you agree with the ruling, it was an official ruling from a CASA representative, enforced by CASA, regardless of anyones personal interpretation. Personally, I agreed and had warned this person of their folly.