I agree with the use of the dumbbell spotters after a certain point. When you have powerlifters and strongmen using 150lbs + dumbbells it becomes a pain in the ass to position, spot, and balance them both for the lifter and the spotter. These will save time and energy that he can use to actually use to make the lift.
It's an interesting but not absolutely necessary piece of equipment, sorta like say, bumper plates.

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