I think that one needs to define what they mean by "simul-climbing".
I have never considered traveling together with coils or on a shortened rope over Class 3 or 4 terrain as simul-climbing. Rather just as an expedient way to avoid taking the rope off and having to tie in again when further difficulties are encountered.
Seems to me that the current meaning of simul-climbing is moving together over Class 5 terrain and placing intermediate protection, but not belaying.
Am I correct?
In either case, I have always believed that if I feel the need to place protection, I am admitting to myself that there is a chance that I could fall. If there is a chance that I could fall, I want a belay. My policy has always been and will remain that if the leader is placing protection, there is an old fashioned, stationary, protected belay.