I think it would have trickle down effect, but then you would have young adults being pushed out of D2\D3\NAIA until you get to the point were there would be people that would have nowhere to go.
It is almost like the NAACP, national leadership, did not think things through before announcing this. As the numbers are not on their side.
I wonder if a better idea would have been to target specific schools and a specific sport in a state where the black population is high and having a fair redistricting process would result in more seats across the board that would favor the black population, generally speaking, interests. The NAACP would need a funded NIL piece to this, as you would need to support the young adults who join the boycott and they should not put the pressure on any HBCU school or schools to come up with NIL monies for boycott the NAACP called for.