Ezreal's Q can gain a stack of Fervor, but can't gains stacks to Rageblade

uh what? braum's passive stacks on- hit not on spell damage so of course it would stack it

It's the same thing.

purely for semantic clarity, a basic attack IS the same thing as an auto attack ezreal's Q is only TREATED as a basic attack for the purpose of a basic attack's on-hit effect. it casts as an ability, because it's an ability, and though it doesn't trigger spell effects anymore, it still triggers ability (casting) effects such as sheen.

to clarify, since somehow i got downvoted for this: an auto attack is a basic attack. ezreal's Q, like miss fortune's Q, is an ability which is casted and has a component that functions "as if a basic attack" - specifically, it applies on-hit effects AS IF a basic attack. It's not a basic attack, however, because it scales separately, cannot crit, has a separate casting animation and a cooldown, and triggers "on ability cast" effects such as sheen which basic attacks (synonymous with auto attacks unless you've turned off auto attacking) do not trigger on their own. And, most relevant to our conversation, it lacks the basic attack windup that would interact with "on attack" effects. ergo, not ACTUALLY a (flipping) basic attack, just an ability that applies basic attack onhits like lifesteal instead of spell ones like ludens, thank you, good night example of an ability that IS, at least in portion, an actual basic attack: twin bite. The basic attack that triggers twin bite can crit, and your basic attack timer is reset in order to use the ability - unlike mystic shot.

if you're talking about the OLD (pre-rework) guinsoos, that used to stack on spell cast and basic attack. Guinsoo's mechanics have since been reworked (along with the whole rest of the item, if you didn't notice) and that's why you're seeing the difference now. just so you know, it's being reworked again.