^the theory on either x and h pipe is that it creates a scavenging effect where the air in the adjasent pipe is sucked out creating a slight underpressure.
This would help sucking the combusted air out of the other cylinder bank when the exhaust valves in that bank open.
If this is still effective in a turbo engine I dont know. There a turbo wheel/wastegate blocking that underpressure.
Its something that should be measured. Still even in a turbo car the exhaust air is still pulsated, so resonant adaptations can influence that.
Maybe they added the x-pipe mainly for sound experience; that was another benefit concluded in the video
