I've discovered that with a good lap job to take off the rough edges that is pretty much a myth as they clean up pretty much the same as any other barrel. Hot soapy water dissolves black powder fouling very thoroughly pits or not and wiping between shots with a spit patch will maintain accuracy as long as patch integrity is not compromised.
I hate to see pits in barrel steel probably worse than most being gun school trained but after learning how to lead slug lap, getting a good borescope and plug gauge set I had to change a lot of gun school taught notions that did not turn out to be universally true lined up against actual experience. Truth is, if were honest about it, we never reach the end of things to be learned in this craft!