So far as I can tell (though I've already been wrong about RB and RC today), the people who are classifying these are now doing so by their delivered configuration rather than obvious numbers painted on the engines themselves as in the past. The engines themselves are interchangeable between RB and RC as of Booster 7's flight, and indeed they have been so-changed:
See for example Raptor 93, described in the "SpaceX Raptor 1-100 tracker" (found from a tweet by SpaceRhin0 embedded in this NASASpaceflight.com forum post by robot_enthusiast) as
Was seen at the build site on [July 22 2022] as an RB, seen installed as an RC on B7 [Oct 10 2022]
The same forum post makes this claim:
The majority of engines are delivered in the configuration that they are intended to be used, but if plans change it doesn't appear overly difficult for them to make the switch. As far as I can tell, the only difference is the presence of the TVC arms and the assembly bolted to the top of the engine which interfaces with the vehicle. On an RC there are hinges in the top assembly and 100% of the plumbing is passed through. On an RB the assembly is a solid piece, and the plumbing for startup is routed to a panel on the side of the mounting bracket rather than being fed from the vehicle.
I chose that post because it's the most recent result in a Google search of NASASpaceflight.com for "Raptor Boost", from Oct 17 2022.
The usual disclaimer about these not being official sources but instead being a community drawing conclusions from the photographs they can take from outside the fence applies, but on an admittedly brief skim I believe that robot_enthusiast's post isn't controversial among those folks doing these observations and that the open-source intelligence work being done on that forum is grounded in physics and displays understanding.