An IR(R) holder who has gained 15 hrs instrument flight time as PIC on aeroplanes (not simply 'IFR time'), will also have flown 15 hrs instrument flight instruction time for the IR(R).
No, not necessarily and, in my opinion, actually rather unlikely.
An IMC/IR(R) course requires a minimum of 15 Hours of Instruction, of which a minimum of 10 Hours must be Instrument Flight Time (flight by sole reference to instruments in old parlance).
So quite possible for an IR(R) holder to only have 10 Hours Instrument Flight time under Instruction during their IR(R) course.