The manual is downloadable from the Well Tempered Web site. But I don't know whether it contains the answer to your question. Might give it a shot if you haven't already.
I owned a Classic for many years. There was no plug on that unit or any WTT as you describe. The tonearm wire went from the tonearm and was hardwired to a connection inside the plinth and exited to an RCA jack on the back of the table. You were able to use any interconnects you chose to make the final connection to your preamp.This was a hard and fast design of WTT from the beginning I believe. I don't know if Bill Firebaugh has changed that since taking over the company. It would seem to me he would not since he designed the table from the beginning.