* finger movement VS arm movement (planted palm VS lifted palm)
* flat fingers VS arched fingers (palm VS claw stances)
* forward/high positioning VS back/low positioning (different approaches to clear the palm rest)
* level wrist VS angled wrist (thumb or pinkie can be similar height off the mat, resulting in positive angle or different resulting in negative, even, or further positive tilt)

All of these ranges exist to some extent within other grips, but I think they’re more pronounced with fingertip because the extra free space between the mouse and palm gives more room to make or break the ergonomics for users’ individual preferences.

It may also be worth noting that the carpal tunnel problems tend toward those users who use a lifted palm as they’re using their wrist more. If the palm is planted and the hand is in an ergonomic position, moving the mouse in fingertip style induces less stress on the tunnels than typing on an ergonomic keyboard.