Specific gravity dictates a material's weight in relation to its size. There should be no debate on whether ferrule materials are heavier than maple, because it's fact. Anybody who doubts it can cut a piece of maple & ferrule material the same dimensions & weigh them.
There should be no debate on deflection, either. It's not a perpetrated myth. It's 8th grade physics. The area I will concede some ground on is in exactly what factors in to cue deflection. I don't believe it's as simple as tip end mass, though I do wholly accept that tip end mass is a critical factor. There is absolutely zero doubt that when the tip touches the cue ball off center, the ball moves one direction and the tip moves the other direction. That's deflection. It's real. The Earth isn't flat and we did put a man on the moon.
Given that tip end mass is a factor, and ferrule material has higher specific gravity than the maple from which the shaft is made, it's only logical that minimizing the amount of material used will thus minimize the amount of impact it has on cue ball deflection.