Yes is the short answer; would there have been 5 miles, no; would the VFR have penetrated class C without a standard being available, yes; would there have been an RA if the turn didn't happen, no; what would have been the distance between the C421 and the 737? about 1.3 miles by plotting it. Seems safe enough; but the C step was fast approaching, no clearance was available; can't turn left, due pucka, must have turned right to avoid a VCA... Was it ugly... yes.
Did the ATC do the right thing; hindsight is wonderful... At the time definetly yes, the subsequent enquiry found they didn't hit, so he did didn't he?