Since this feels the appropriate time, I'd like to chime in, seconding Julie's concerns. I know I was brand spanking new to the game in October, but I believe this incident would have been before the new activity check rule was instated wholesale, yes? Only allowing things to be backdated to the previous month would (seem to) avoid the issue of having things backdated for several months (if that's why the policy was created), with the added bonus of encouraging participation in gamewide events even if one is strapped for time.
So anyway, for the reasons already mentioned, plus for pure simplification, it makes sense to me at least to make no distinction between what can be backdated to the previous month and what can't be.