I've always assumed it was because shadow jumping requires stealth to activate, so it will not allow you to jump onto a tile that is blocked in all directions so that you cannot enter stealth to jump out should you be revealed or log out and back in in that place. Sure there is the "help stuck" menu, but why not avoid the situation altogether, not everyone has magery and or the regs/lrc to teleport out if they get stuck shadowjumping. Of course, I could be totally wrong, maybe the devs overlooked something when adding ninjitsu.The max distance is the same, but teleport seems to have a higher tolerance of z-axis differences between the source and destination tiles or something to that effect. Is there a reason for this?