It gives vision where you place it, only for the time it's up

I use it most to either do what he did and gain vision for ult, or use it by the walls around jungle monsters for escapes (the raptors, gromp, and krugs are really useful

You don’t recommend builds, builds are situational….

It's not a bug or glitch bro, if you look more closely when Yasuo uses ult while enemy under turret mostly Yasuo will suppress his enemy outside from the turret range because it was programmed like that but if the enemy is in the middle of the turret range then Yasuo won't be able to suppress his enemy outside turret range. And about the runes the reason why Yas can't activate the runes passive is bcause he's out from his range which means his 1st ability didn't reach that tris, usually the runes will get triggered since Yas 1st ability is counted as basic attack and empowerment can only be active by basic attack as well