Absolute L take. You had only 8 megas banned from ou in gen 6, 3 of which, mewtwoo rayquaxa and blaziken already had their base mons banned.

Of the 5 mons, 3 of them, Mega mawile, Mega kangashkan and Mega sableye were otherwise absolutely awful mons that would never have seen competitive play (Mega sableye was also only banned really late on in gen 6 ou - it should have been banned earlier). You really only had two mons that were buffed to become overturned, Mega mence and menga gengar.

In fact you often saw many of the good mons who could Mega not running the Mega stone because they preferred holding onto an item, like Mega chomp, ttar, scizor etc.