In https://fedoraproject.org/wiki/Packaging:LicensingGuidelines, it is stated the license file must be included in the %files section using the %license macro.
In https://fedoraproject.org/wiki/How_to_create_an_RPM_package, it is stated %license is not a valid prefix (which I suppose is true, but kind of confusing as it is the only reference to %license in that document) and in the '%files example' section, the LICENSE document is included using %doc macro, which I believe is wrong.
And lastly in https://fedoraproject.org/wiki/Packaging:Guidelines, there is no mention of %license whatsoever.
The rpm creation page isn't part of the guidelines and should be open to editing by all. FPC isn't responsible for it, so feel free to edit.
The main guidelines don't explicitly list everything; the page would be far too long. Instead they refer to other pages that have the full details. In this case, there's a section near the top which refers people to the licensing guidelines: https://fedoraproject.org/wiki/Packaging:Guidelines#Licensing
All of the sample specs in the guidelines which include a %files section should have %license; if that's not the case, just point them out and we'll fix them.
Otherwise I'm not sure what you're asking FPC to do here.