Plumbing in a bypass for heaters is a very new thing in the pool industry. I believe it was Jandy that started it with their versa-flow bypass for their heaters. Does a heater add head to the system? Some, but all new heaters for the last 25 years at least have design flow rates that accept the full flow of properly-sized modern pumps, even single speed models. When you use a VSP, as you have, slowing the water down means that the restriction through a heater has far less effect.
There are a few in our area plumbed like that, I'm local to you. One of my main concerns with a bypass is that, when it is shut, not all the water may drain out of the heater. A bypass has to be plumbed correctly or water will reverse through the heater outlet and fill the heater. If it sits long enough it will evaporate and leave a bunch of "stuff" that is in the pool water inside the heat exchanger. The TDS of your water won't be dissolved any more and that stuff can stick to the copper, titanium, cupro-nickle, whatever. Second, we do get freezing temperatures here. Your pumps have built-in freeze protection that will get the water moving to help prevent freeze damage. If it is not moving through a heater that has a closed manual bypass, and the heater has water in it, you really don't want to know what a frozen heater costs to repair, especially that ETI.
