Engine Masters - X vs H vs Straight Exhaust

I'm sure that would show right up on the AFR gauge if they used one.

My only guess is, a bit similar to the dented header test, what if the two seperate exhaust tubes were already big enough for the engine in the first place?
No real improvement would be expected whatever the crossover would be.

I'm thinking maybe some benefit would become visible if the exhaust was on the small side to begin with, and combining both pipes with and H or X could show more beneficial.