>>29407394they do with traded pokemon though? realistically they should lower the amount of experience gained from trainer battles if you want a level cap which would force you to grind.
the new pokemon games are going to be the same, the amount of exp you get from trainer battles is meant to work with the exp share to allow you to raise a balanced team of 6 mons easily.
i think that makes it your fault if you use 3 and get overleveled. you should try never having less than 6 mons on a team and keeping the exp share on, i'm sure it'll be more balanced than whatever it is that you have been doing.