I finally got around to looking this up in the regs. I believe you are entirely correct. The part on the all-lead bullets, etc. Is under weapons restriction area. In the section discussing the use of firearms, ML's included, there are no restrictions placed on the ammunition used. Good to know.Just picked through the regs.
Any restrictions on muzzleloaders pertains to management areas which have weapon restrictions. Didnt bother to follow up with the Gallatin valley which I think falls under a weapon restriction zone.
I periodically hunt a BMA which states weapon restrictions "archery,shotgun,muzzleloader and traditional handgun". I interpret this as allowing any form/combination of muzzleloader hunting such as,in my case,an in-line with sabot.