They don’t need it to be 3x in store only. They will also rank higher in tournaments for more drops too and likely in higher alliances for war wins and chests (again another source)
I did state 4* isn’t as bad if shape close to equal (obviously depends on season, costume bonus, etc), but older 5* will suffer the most with the % method.
I don’t know why you feel a need to defend this system, it is far from perfect and could have been made in a much better way even if it was non-negotiable. Specifically fixed stat gains alone would have been an improvement over the % method. Also restrictions on what could be limit broken, etc. But the main thing to mean is it adds nothing new, just more stats, like make it do something else like a small Mana % or something to make it unique… That’s the biggest thing limit breakers are lacking IMO, something unique about them.