It was a general question worried about breaking 9s, actually.
And I 100% guarantee you that the Yngwie strat wasn’t “designed” for a particular brand or gauge of strings. Yngwie likes 8s, but if you like 9s or 10s, or even 7s, you can absolutely use them on his guitar. He personally likes 8s, and that’s fine, and if you like 8s, that’s fine too, but you’re absolutely not going to hurt anything if you threw a set of 10s on, and if someone wants to play his guitar with a set of 9s through a Mesa Mark IIC+ and digs the sound they’re getting, then it’s not on us to tell them they’re wrong - we can all do whatever we like, because since we’re not Yngwie, we don’t have to exactly mirror his gear choices.
Heck, my favorite singlecoil pickups are Suhr ML Standards, which I guess are a Michael Landau signature set…? I don’t think I’ve ever even heard the guy’s playing, the extent I care is I picked up a Suhr with one in the neck position, loved it, and bought a set for my go-to strat. And they rule. I have no idea what strings he uses or what amp he plays into or what pedals he likes, all I know is they sound phenomenal through the amp I like.
Use whatever you like. It doesn’t matter what a particular celebrity uses, since none of us are that exact person, and we all have our own preferences.