the tagging for NSF files are super restrictive; it's like, 3 things. Song name, writer, and copywright I think? So al the tags you assign in foobar usually do nothing because almost all of them literally cannot be applied to the file. (also where's this setting in foobar to enable writing? can't find it)
Edit: nvm, found it
Edit2: As a note; many people dump nsf files from actual nes games themselves, and want to make sure the hash checks out. Might be a reason why? Although it seems strange that it only does that to nsf specifically