The Client changed the Rules to require a Second Pilot.
The client can require whatever he likes-this has no influence in crew designation.
Only the Operations Manual an/or the certification of a helicopter make it a single or dual pilot aircraft...
If you are flying a Bell 212 (Single Pilot as per Flight Operations Handbook, and i bet it was single pilot in accordance with the company operations manual as well), it is a single pilot aircraft-no matter what the client wants.
If your boss puts two pilots into this single pilot aircraft, it is still a single pilot aircraft, hence the second pilot can not log those hours.
Reason for this is simple:
A twin-pilot aircraft has higher requirements than a single pilot aircraft-all instruments need to be installed AND working, and the crew requirements are higher as well (MCC, ATPL.....vs. CPL).