I think its still worth a scraper
the oil clings to the crank adding to its mass and in times of surge adding to its mass unevenly (one end or tother) which has a small but adverse affect on the crank i.e can add to harmonic vibration i.e minute harmonic twists along its length
anything that takes off the big gloops reduces both oil mass on the crank and aerodynamic drag. pointless having a nice smooth crank with knife edges if its coverd in treacle
any big gloopy area spins the oil into a cloud which travels onto all surafces of the crank along its length adding again mass to the rotating assembly. stop big wet areas = stop adding to the cloud of oil in the sump means crank turns more freely through cleaner air
they also help control oil movement caused by the considerable amount of air shifted round by the crank as it spins. i.e cut down on the hurricane affect i.e do the same thing as a windage tray to some extent but by different means
these are supposed to work wonders on a hemi 6 with its long bendy harmonic afflicted crank.
This comes from the same school of thinking as having the inside of your engine/sump painted with special heat resistant but very smooth almost teflon pan like non-stick paint (no not the bores or bearing saddles .....

)
caveat
all of that stuff above comes not from experience but from having read some stuff so it may be Bananarama!
Dave