Au contraire; closing the valve reduces the outflow, thus the WORK the motor is doing. Same with a vacuum cleaner, that high whine you hear when the hose is plugged is the motor revving up because of REDUCED work load.
I never got a third reduction in my bench tests on pumps, but valveman will give you his much longer experience in restricting the flow of submersible pumps. Some more, some very little. But the rule is reduced flow means reduced load. Now, if you reduce to zero or near, you will overheat the pump "deadheading" and burn it up or shut off the high temp cut off. The water isnt going anywhere its just revolving in the stages and making heat from friction.
If you want maximum EFFICIENCY, you carefully design-choose your pump- to work in its sweet spot [BEP- best efficiency point] most of the time. No so easy and requiring a lot of understanding of pumps and tanks and patterns of use, that may change with the owners and seasons.
This is regarding CENTRIFUGAL pumps, and other rules apply to the hundreds of other types made
Maximum current draw in a centrifugal pump occurs in high flow no head situations. Low flow, high head causes the opposite.