If not GameFreak is stupid...
I did some Eviolite testing for The Immortal and Kris, who had requested this earlier, but I got distracted with other real life things. Original regional forms of Linoone, Mr. Mime, Farfetch'd, Corsola are unaffected by Eviolite. Gmax Eevee/Pikachu/Meowth are unaffected by Eviolite.
I’m pretty sure they’re counted as separate forms in the games data, which is how previous generations avoided Eviolite boost on say Cap or Cosplay Pikachu. :P
Source, EXP
Hope I helped!