Most don't realise, even shooters. The jump is minimal, I mean, it's not like an inch or something.
Some rifles like it nestled right up there, some don't. My 6.5mm creedmoor doesn't mind a bigger jump. Besides, with the projectiles I use I can't minimise the jump much as they don't fit in the magazine. My .308 on the other hand...Smaller the better. I only have 20 thou in there for safety purposes, a buffer. I'd run it right up to the lands but again, the magazine dictates maximum length.
Sometimes running it right up at the lands can cause more back pressure and with larger calibres that can be dangerous. Most guns it doesn't matter if there's some jump though but for long range shooting it is often best to plat around and see what works best. I tried different seating depths and determined 20 thou jump to be the best.
Running it jammed up also causes issues if a round has to be removed prior to firing but after the bolt closes. It will often pull the projectile out of the case and pour gun powder all over the place. Most long range shooters run very loose neck-tension to impede the bullet less when fired.
It's interesting though huh?