The more flow through the panel the more pressure rise you will see and flow through solar panels is a good thing. Panels transfer more heat to the water, the faster the water moves through the panels.

So if you are bypassing too much water around the panels, they will not work very well. With solar panels, if the flow drops too low, your efficiency will drop and you won't be heating the pool as quickly. There is usually a minimum flow spec depending on the types of panels. My spec is 10 GPM/sq-ft of panel which means that I should not drop the flow rate below 48 GPM.

So while a high PSI does mean you are increasing the time to turn over the pool, it may be a bad idea to try and reduce that too much. My PSI rise is about 7 PSI although I too have a bypass so I can lower it to 4 PSI but I have done the head calcs to make sure I do not drop the flow rates below optimum.