I know the feeling! I'm playing a Town Jump game and randomizing the traits and I've had multiple artistic and virtuoso sims, which can get tedious after awhile. And the heirs are supposed to complete unique LTW's.
So, for your ops did you actually see where other instruments counted?
I'm wondering if the Wiki mentions the Bistro because that's where more guitar ops come from, rather than the ones for other instruments?
My heir sim has maxed her guitar skill and painting too, yet another artistic, virtuoso, and since I'm not playing a dynasty, I can see if I can trigger those guitar ops for the bistro.
I'll let you know how it goes after my next play in that game.
Though that may not be soon enough to do you any good in your dynasty, it would be nice to have accurate information going forward.