I use a pipe in my HT forge, my system is heat forge up to high temp fast.
Takes about 10 mins or more, next put in my pipe and allow pipe to get to high temp.
Next lower PSI to about nothing, just where the forge is barely running and shoot for desired temps. I personally use a Thermocouple.
Next put in knife and let get to temp, then Quench.
I used to not use a pipe and I got serious hot spots. With pipe it really evens out my
temperature.
All depends on forge being used I would assume though. I do think if my burners were at a tangent I would not need a pipe.