Anyone mix 87 and 93 octane gas to make 91?

Heard of doing this. I've always put 100% 93 octane. I guess on paper it makes sense to me, but would they blend together? Or would you get some 87 coming through then some 93 coming through then maybe some 91 coming through that got mixed up?

Or do they just blend together to make 100% 91 octane?