This was during the summer of last year so weather not really an issue, I suspect they were merely making it clear not to turn up with expectations of getting lots of flying done.
I totally understand that to keep costs low etc everyone is expected to help out which I'm more than happy to do. I would however be pretty miffed on a cracking day to have not got flown after a full days attendance when I have my own aircraft sitting in the hangar that I dont get chance to fly enough as it is!