That can't be the case, as I just caught one with over 200 HP and 150+ attacking stats. Maybe those are the stats assuming 0 IVs?
Right, here are the legit max stats:
HP: 201
Attack: 151 (neutral), 166 (+), 136 (-)
Defense: 115 (neutral), 127 (+), 103 (-)
Sp. Attack: 151 (neutral), 166 (+), 136 (-)
Sp. Defense: 118 (neutral), 130 (+), 106 (-)
Speed: 119 (neutral), 131 (+), 107 (-)
To calculate by hand, the formulae are:
HP: (IV+2*BaseStat+EVs/4)*(Level/100)+10+Level
others: ((IV+2*BaseStat+EVs/4)*(Level/100)+5)*Nature
where Nature is 1.1 for increased stat, 0.9 for decreased stat, and 1 otherwise; and Yveltal's base stats are 126/131/95/131/98/99
Also, another question of my own (I have the Lucario matter settled), I know it's the case when Super Training, but is it also with regular EV training that a stat cannot exceed 252 EVs? Wondering because I might want to try the Horde Battle method.
(sig cutoff prevention)