Essentially yes.
What do they achieve? On my system, not a great deal. It was an idea Heat Geek had about how having two 'smart' pumps essentially in series would confuse/upset the pumps as the effect of one pump responding to feedback from its circuitry would affect the other pump and reduce their lifespan and I wanted to try the CCTs to see what happened. I hadn't originally put CCTs in as I was of the opinion that the UFH would essentially only take what it needed from the primaries, and so it seemed to. Whether the pumps will last longer is impossible to say as there is no control experiment.
I can see they might be needed if the maximum flow through the UFH exceeded what the system pump or boiler could allow, but as my boiler is running at 12kW output (IIRC) and my UFH load is around a tenth of that (between 1 and 2 lpm), I suspect the question is academic. If they do anything, I suspect they extend the UFH warm-up time but reduce the radiator warm-up time when both zones call for heat in the morning.
