>>23272425The first fairy move that a wild-caught Eevee could learn in XY (Charm) was one of the better moveslot choices for Eevee at that level. Most players who raised a captured Eevee to that level probably did choose to replace Growl with Charm
When the evolution result was a Sylveon, GF probably expected that players would try to recreate the evolution, and that (after just leveling Eevee up with just the Amie part and likely winding up with an Espeon or Umbreon) we would hone in on the only other circumstance unique to Sylveon's evolution (the fairy move)
It's not intuitive in any way, though. I don't expect anyone would have gotten one on their first playthrough (except by total accident)