Thought experiment:

Think of a normal 3 phase motor, with 3 sets of windings. Now imagine
that each set is only 1/3 the length of the rotor and separate axially
from the others (a set on each end and 1 in the middle). But still
having the same angular position. Very inefficient, but nothing's
changed magnetically, right? Further imagine that the rotor is divided
axially in three sections and each section is magnetically isolated from
the others. Each set of windings is still producing the same time
varying magnetic field, with the same phase relationship to the others.
Each field is still having the same effect on its section of the rotor
as it did on the rotor in the integrated motor. Overall the rotor is
still experiencing the same magnetic force.

This is equivalent to Eric's 3 separate motors with connected shafts,
isn't it?

Bob