When I caught one of the Gible in Zone Zero, and put it in my party by sending another Pokemon to the PC, it evolved immediately after the battle ended.
Not sure if that's a bug or not, but sharing anyway, just to be safe.
I'm gonna go out on a limb and guess that the Xenpurgis may have had something to do with the nuclear explosion in the Miera region that Erin told us about, and that the surfboard guy with the Xurkitree may be part of it.
There actually used to be a Rare Candy vendor on Route 3 before V11, but I guess someone realized that you could farm the Solrock in Amethyst Cave for Stardust and the occasional rare Comet Shard, and Jan found out about it.
Because it's got the highest base HP of the Eeveelutions, capping at either 444 or 454, depending on whether the Eevee has 10 or 20 IVs across the board.
Edit: I forgot about the level cap being at 85 when I posted this. It's HP stat can still be very high.