The short, stubby saddles are designed to keep you supported in one position, without accomodating very much movement fore-aft. If it's causing no discomfort, pain or injury, it's doing it's intended job. Longer, more traditionally shaped saddles accomodate more forward-aft movement on the saddle, but I don't know if I would rate the saddle disappearing under you as something desireable, especially from the point of view of comfort over long rides.
I can lift my backside off the saddle and move to the rear when descending super steep stuff, but not quite "slide" behind it.
As for positioning forward and back, I experimented on that by well, moving the saddle. Too far forward and the bike becomes unstable, and taking hands off the bars becomes a chore. Moved back, putting out power while in the drops on the flat becomes weird, although it feels fine on climbs. However, while the feeling is different, I can develop the same power unless the difference in position is dramatic (eg. switching to a TT bike where there's a huge difference in seat tube angle and saddle position vs a road bike plus a big difference in hand position).
Last edited by Branko D; 01-20-21 at 03:15 AM.