Broz
WKR
I don't know, I'd guess the common assumption is that it may hurt velocity.
The velocity loss in faster twist barrels is so small I am not sure it is detectable if it even exists. There is a lot of data for Cheytac improved velocities out there and with the transition to tighter twists a lot of this data from trusted sources at different twist rates with same weight bullets. My new 375 ELR sends 400 gr bullets at 3150 fps with a load just under max pressure. That is among the highest velocities I can find data for. And it is a 7 twist. My 300 win mag same length barrel as my 30 Nosler. 300 win is a 10 twist, 30 N is a 9 twist. Both rifles, side by side hit exactly the same velocity with exactly the same powder charge of N-570. Again zero evidence of velocity loss. I use to think this made sense too, because I heard it some where. But today's actual data pretty much proves it is more myth than not.
The barrel availability issue is real. But it is changing. It will change faster if we do not "settle" for barrels that are not offering us top performance from our bullets.
Jeff