It can be done if you ac requires a 50 amp max breaker and the wire from the smart switch is three wire to ac unit. Then the electrician changes the the wire from the panle to the smart switch from three wire to four wire. Then run your four wire to the RV plug.
Not saying it's what to do just saying it can be done.
If max fuse/ breaker was 30 40 etc then supplemental would be required after the smart switch to protect the existing branch circuit conductors.
In this example a fused / breaker ac disconnect would satisfy this requirement.
This would make for a pretty ugly install.
My only issue by doing this would the branch circuit now become a feeder based on tap. Would any tap rules apply. Or is this simply a shared load on a branch circuit.
Would this no longer be a dedicated branch circuit.
So now it's time to start reading what code might apply to an install. In order to be code compliant.
New twist on the old add a wire to the dryer recpt poke thru wall and add recpt for compressor or hook a cord into the ac disc for the RV in back yard.