It's fundamentally different from trickle down economics. It's about finding the point between 0% (which would raise no tax revenue) and 100% (which would also raise no tax revenue) which would provide the maximum tax yield. Seeking the maximum yield should be seen as a good thing to someone left leaning. One can disagree about if that maximum point is at 80% or 40% or in the middle, but it's nowt to do with trickle down.
It's about coming up with a justification for letting the rich keep more of their money. Same as trickle down.