I agree.True, you do have to shoot a lot of rounds to get enough buildup to make putting rounds in the cylinder tough, but I have had it happen. Maybe I was using dirtier powder....IIRC I used 700-X in .38 and Blue Dot in .357.
But like entropy, I've fouled the chambers of my S&W 610 with 3-4 cylinders of 40 S&W rounds such that the 10mm rounds would not chamber.
I cannot say that I ever remember having chambering issues after shooting 38 Specials in my 357 Magnum Model 19.
It is a nice feature to be able to shoot several different cartridges in a gun.
But, since I reload, I can tailor my reloads to any level and I do not need to shoot the shorter cartridges in guns chambered for the longer cartridge.