Why not just call it a masonry heater? When I talk to people unfamiliar with the technology, I explain mass heating in general, show them a masonry stove, then tell them a rocket mass heater is the diy version of a masonry stove.
In the multiple names for this tech, you see 3 variables: the core descriptor which is usually “mass” or “masonry”, the thing (usually “heater” or “stove”), and then an extraneous word to describe the style “Scandinavian” or “Russian “ or “rocket.” For code inspectors you don’t want or need a new style to confuse them, you want it to blend in. Like instead of saying “straw bale” calling it “fiber insulation.”
If super-nice masonry stoves became more popular, then lots more people would want the less expensive diy version. RMHs aren’t popular because no one has heard of mass heating technology.