More like Trace thing. Wishiwashi has the ability Schooling which causes form change when attacked, Calyrex has As One ability that allows it to 'fuse' with either Glastrier or Spectrier; both abilities cannot be Traced.
But on the last panel, Joltik has the Compound Eyes ability, which can be traced. Same with Marill's Thick Fat, Yamask's Mummy or Sligoo's Hydration.
