Except that RAAus aircraft (such as Ross' Sportstar pictured) operating to CAO 95.55 are exempt from compliance with CASR, says CASR 200.14.
91.410 does not apply. Crashing would be perfectly legal.
Ross, you made a good call. You chose to not blindly follow the advice given because it was a bad idea for you - when you got there.
Maybe you could have used the grass perfectly fine, but you didn't 100% know that at the time you were there, and your airpersonship voice told you "NUP, not doing it, no big deal, I'll just go home." Good call. Maybe over cautious, but so what?
It all depends on what was asked or said on the phone:
"we are using runway 37" (as in now, while I'm telling you. But later, who knows!)
or
"you must use runway 37 only because of (whatever)"
Perhaps ask a few more questions on similar PPR calls. Cover all bases. "Is the grass runway usable too?"