The term Robot Master is kinda sketchy when used outside of the 8 bosses, and as it isn't used in the cartoon, who knows? It's up to your preference, as they are humanoid robots with (at least 1) weapons that can be copied. However, it should be noted that in the spider robot episode Mega Man is shown to be also able to copy/steal other things, taking a copy of the robot spider's web data to bring it to Dr. Light. And outside the cartoon, he got data of the location from Wily's hideout (MM1) and a virus (MM2) in the Archie Comics. It can be debatable, like Auto, Plum and Sniper Joe.