>>26695178First of all they built the game, so they can edit the ivs and evs with less effort than you can.
65 base hp has been confirmed by source, because, like I just said, they CAN edit the stats.
Just because they haven't before, doesn't mean they can't.
>>26695229It's a wild guess, because at base 18 :0 Atk Garchomp Dragon Claw vs. 0 HP / 0 Def Zygarde: 98-116 (125.6 - 148.7%) -- guaranteed OHKO
18 and 65 are values that logicaly fit that hp stat.
I already said that they are most likely not INCREASING its defense stat, so they decided to buff its hp, "conveniently" giving 125 like in the picture.