It needs to be good flow over bad compression, but I agree. I’ve seen it go both ways, but 99% of the time if you have to lose some compression for flow, it’s a win.
Now, if you do something to that gives up compression and the reverse flow gets worse (better as it may be said) then you can lose a ton of power at and around peak torque. Which should be right in the gear change. Which is an ET killer.