Not so I'm afraid
There were 3bar Captains as late as the early 80s who did not have I/Rs. One Pilot 3bar Captain
It was only full ATPLs (so with I/Rs) that were allowed 4bars. In larger aircraft that needed two pilots!! Two pilots 4bar Captain!
Thats why it became a joke to see single Engine VFR Helicopter pilots wearing 4bars. Yes Egos indeed. Now you see 4bars comming out of a Robinson!!