Sepp
Maybe I've missed what you're driving at, but to answer your question literally;
Obviously, SPA turbo-jets and a/c subject to a type rating require two qualified pilots under OPS, but is the B200 not an SPA, operated under a class rating?
No. It's a SPA operated under a Type Rating on account of it being a multi-engined turboprop. The difference between it and the aircraft you mention (Seneca/PA31) is simply the type of powerplant.
It is not the only aircraft designed and certificated to be operated by a single pilot that requires a Type Rating in JAA/EASA land. See also Twin Commander 690/695 series, GAF Nomad, early model PA31T Cheyenne etc... turbine powered. (NB the Cheyenne; a TR is required for this turboprop derivative of the TR-less Chieftain, the latter flown under MEP Class privileges).
But I concede that I've probably missed the thrust of your argument...
ref:
List of EASA/JAA Class and Type Ratings, whether JOEB'd or non-JOEB'd
edited to add: Cheyenne/Chieftain bit