I wasn't on the stream, and I don't know the physics of the object ball gaining weight, but from what you say about the cue ball glancing more as you hit it harder, I would imagine he's talking about the cueball's tendency to follow the tangent line for a longer distance before top or bottom spin take effect on cut shots. When you cut a ball softly with a lot of top spin, the spin will take effect much sooner, as opposed to hitting it harder where the "curve" is wider.
You are 100% correct. Danny knows a lot, it is unfortunate we lost a lot of good advise from him because at times he confuses the color of the balls, i bet you those balls are not coming back.