I am perfectly fine with their choices of Fairy type retcons. All of them were either single-typed Pokemon that got Fairy added as a 2nd type(Igglybuff/Jiggypuff/Wigglytuff, Mime Jr./Mr. Mime Azurill/Marill/Azumarill, Ralts/Kirlia/Gardevoir, Mawile, Cottonee/Whimsicott), or a Normal type that had it's Normal typing swapped out for Fairy(Cleffa/Clefairy/Clefable, Togepi/Togetic/Togekiss, Snubbull/Granbull). They intentionally left out ones that could potentially be overpowering(Chansey and many Single-typed Legendary/Mythical Pokemon) or would require swapping out a type that was not Normal(Lots of them I could list that fans wanted, most commonly stuff like like Gallade) so as not to disrupt their STAB options too much. Also for Normal type, which lost 8 Pokemon, they made sure to add exactly 8 new Normal types in Gen VI so at least the number would stay the same instead of going down. Additionally, the only moves to be retconned to Fairy type were three normal-type status moves introduced in Gen II(Charm, Moonlight, and Sweet Kiss) and they simply created a whole line-up of brand new damage moves for the type.
I disagree slightly on Gallade but idk how much that is just me wanting a new and novel typing in Fairy/Fighting vs the redundant Psychic/Fighting, which it shares with Medicham (and Mega Medicham and Mewtwo for extra redundancy). The fey, empathic qualities of Ralts et al are equally in tune with Fairy as they are with Psychic. But Gallade's Psychic side is rather underdeveloped - it's mentioned in a couple of Pokedex entries, but only passingly:
HGSS dex entry: Because it can sense what its foe is thinking, its attacks burst out first, fast, and fierce.
Shield: Sharply attuned to others' wishes for help, this Pokemon seeks out those in need and aids them in battle.
Only the former explicitly suggests Psychic abilities - the latter only really screams "Psychic" with context. It could just as easily apply to Cobalion or Lucario. Gallade leans much more into the Fighting side than Psychic, which isn't entirely atypical for dual-typed mons. But Gallade tacks to one side more than most.