Well there are a couple different reasons why you may want a refined control that does not involve a closed loop especially if you have redundancy built in. For example while not the Varios I have redundant returns using a Cor 15 and a Cor 20. I also have a Cor 15 powering my skimmer. Let us say the skimmer failed and for some reason I wanted it online. Although they do use the same connectors I have two to choose from. It makes sense to replace the 15 with the same one so use the 15 on the return. I travel a lot and I'm lazy so my returns are not labeled

I could ask someone to replace it but since they look the same the easiest one would be used. If it was the Cor 20 I could adjust it
I also use a pair of 1" Sea Swirls instead of power heads. One has a longer plumbing line than the other so the Cor 20 goes here, the 15 on the shorter line. Now the fun part is that I created a virtual outlet called Tide. Using the Apex OSC function I set it to go on / off every 6 hours which would replicate high and low tides. On the return pumps I can use that virtual outlet and set the power / percent on each and alternate one side of the tank to generate more flow while the other is reduced. Every six hours they swap out and I get alternating flow throughout the day.
These are the two reasons why I like the control of the Apex. I'm working on another virtual outlet that will randomly increase both return pumps to 100% causing a bit of a sand storm but this still needs work