You can but if the resin level is above the top edge of the mold it makes it more likely that some resin will spill as you move them into the pressure pot. In my experience the pressure pot doesn't actually affect the level by a noticeable amount unless you have . Some resins may contract more than others while curing but that's a property of the resin and isn't affected by pressure.

In most cases I find it easier to deal with any potential shrinking after the item is cured instead of trying to prevent it. Most of the time the level is fine and doesn't actually need topping off so I just use a deburring tool (example here) or craft knife to remove the lip and smooth the edges down since those spots can be fairly sharp. In the cases where the level is too low I will do another small pour to top it off before I pull the item out of the mold.