We disagree. But I don’t “swim” up or down…nor do I use my BCD as an elevator. I find that it is easy to control buoyancy horizontally, and much more comfortable.This insistence of always staying horizontal is quite disturbing to me: one should stay in the position which mininimzes drag , allowing to swim with minimum effort.
If you are swimming horivontally, then of course your body should be horizontal. But when swimming up or down, the body should be vertical, either head up or head down.