Mikey,
I don't know anything about the specs for NFPA, BUT, there is a company in my area that had a couple of welders who were only qualified to AWS D1.1 pipe specs. The only people normally challenging them on anything were the local City and/or County inspectors here and all they asked them for were any kind of pipe certs on their people doing the in shop fab or field installation.
Now, it is all really dependant upon what the EOR calls out in the print pack, general notes, and/or Job Specs and Contract. Somewhere in all the bounty of information should be the info on what the welders for that part of the job need to be qualified to Code wise.
Doesn't help you with what NFPA requires but hopefully is of help to find out what the welder needs for qualification.
Have a Great Day, Brent