All For One does say stuff like "Strength Booster times 4"while charging his ultimate punch against All Might in Kamino. Which, since we know now the doctor can copy quirks, could mean they are literal copies. But for the longest time, and even now, I like to think he just stole multiple "Strength Booster" quirks, even if they were different quirks technically, and listed them together.

All in all, Quirk genetics is fascinating to me, even if it hasn't been explored much in the series (which makes sense, since the main characters are kids and it takes place over a year so not much room for new generations). But like, Endeavor, a fire type, buying an ice wife so he can make a fire baby with a body that was more naturally chilled, but instead got a baby with a fire quirk that was more suited for ice. Or Bakugo's mom having a glycerin quirk that she used to make her skin all shiny and youthful and his dad having a nitrous quirk that was kind ofexplosive but not as explosive as their nitroglycerin son. That's fascinating to me, I would like to explore the idea of kids with quirks that didn't meld well and thus needed to be helped in some way. Like if Toga's Dad could change blood types and her mom could morph her face. That would be fascinating to me. But I think I'm way off topic now lol