OK- good point. Most times people refer to 'different mastering' they refer to mastering techniques that address phase, LF, HF and limiting. Most mastering studios offer 'vinyl pre-masters' for this reason. RIAA is embedded into the cutting rack and not a mastering engineer decision. So perhaps this is a matter of semantics...
I would say that RIAA equalization doesn't really change anything in the sound, since it is counter-equalized upon playback. In that sense it isn't really a change in the master upon playback comparison with a digital file, for example. Provided of course the scenario that reverse equalization on the playback side is perfect, which may be another issue.
Mastering techniques that address phase, LF, HF and limiting specifically for vinyl are changes in the master.