Potions Auto buying 5

I was in a game (ARAM) and went to buy a Health Potion. I think I MIGHT have been holding "alt" and as I went to buy one leaving the fountain I filled my slot immediately.

I quickly thought TIL: ALT click auto buys the full amount of Health Potions you can have.

But didn't get a chance to check it again in game, it ended and I went to bed. Now I am at work and can't check.

So bug or unknown working as intended.

Edit: This got removed immediately after I posted it...so...repost lol without "Glitch" in the subject.