He doesn't even have to play it. Just hold it and he gets the SMV boost.
That's the hilarity of looksmaxing. It's all based on multipliers. A guitar might give you a 1.1x multiplier, but if you're SMV is 2/10 you're at most now 2.2/10, and when you're sub 5 things like this can actually look like "overcompensating" so they might be more like negative multipliers, leaving you at 2/1.1= 1.8/10.
Whereas if you're an 8/10 like that guy, you're now a 9+ when you play guitar.
It's all a giant joke.
That's why you see guys on PUA forums always giving bluepilled advice. Most of them are 6+/10 tall white guys. As soon as they start lifting weights or dressing better or getting better haircuts, their SMV goes up hugely and it really works. You won't see short ethnics giving that advice because it doesn't work when you're sub 5.
Life is a joke.