Vaporeon’s Hydro Pump on defense

In Vaporeon’s page Hydro Pump is over Aqua Tail on defense, the former being an A rating and the last an A-, maybe because AT despite having an early dodge window and being a 3 bar move it doesn’t do great damage, backing from Vape low attack stat, so Hydro Pump being so unpredictable and doing huge damage is kind of better, Vaporeon water gun is a lame on defense but maybe that would be good since it’s damage is so low it doesn't give the attacker much energy to fill it’s charged move, the same can be applied to AT, but in that case AT damage gives the attacker more energy in exchange for little damage, that’s what I think ?