All pool pumps are designed to run close to the rated TOTAL HP (label HP * service factor). So a 2 HP motor with a 1.35 SF will run close to 2.7 THP at the best efficiency point of the head curve. Manufactures usually leave a little bit of head room so the motor may never reach the full THP but it will get close. They can do this because a pump on a pool plumbing system has fairly constant load and torque requirements do not vary much.

Also, most pump lines come in an up rated vs full rated version. So an up rated 2 HP pump (1.23 SF), will have exactly the same performance as a 1.5 HP (1.65 SF) full rated pump in the same pump line. It is simply a relabeling of the motor but the wet ends have identical parts and so the head curves are identical.

So when comparing motors and/or pumps, you need to compare the THP, not just the label HP and not just the SF but both combined. But even that does give you a good representation of the pump. The head curve is a much better indicator of the power of the pump.