The 'pre-sort' points can also be used to simply move the moving parts away
from the intersection where road vehicles may be driving over them all the
time back to somewhere out of the way of traffic.
That way the switchblades and their drive mechanism are not being hammered
all the time.
I'd say that's the major reason for them - move actual point blades
somewhere 'safe' - that will be the reason you see 'trailing' versions, the
actual point is 'out of harm's way'.