I COULD BE BANNED!
Well, Waterfall also has a 20% Flinch rate, and considering how game-changing a random Flinch could be, it's warranted.Depends on what you want on your team, or what risks you want to take. By your logic Azu would be running Aqua Tail over Waterfall tbh.
Also yes G1 transfers have their hidden ability. Gender... I'm not sure tho.
Flame Body Moltres would probably be a interesting second option to offensive variants when it comes in to take resisted hits (i.e. Breloom's STABs, Scizor in general). However, I think Pressure is overall more valuable against many team comps because it severely reduces the longevity of a Pokemon's time on the field, such as cutting 24 PP moves down to 12 and 8 PP moves down to 4.