IMO, flasking right out of the gate is very inconsiderate and weakens the alliance as a whole. It’s less true for alliances fighting 9* titans and up, as everyone at C grade or above gets 3 shots at ascmats according to Revelate’s math (plus the rare titan bonus).
But for the alliances that are fighting 8* for instance, there is a 50% bonus ascmat chance for anyone reaching B grade, and that is made less likely every time someone does more than 3%.
With 6 flags, one can knock 10% of a titan’s life points by onself, thus depriving some team members of the possibility to get to B grade.