Some technical details.....

A sensored brushless motor has 3 electronic magnetism sensors that will see the position of the rotor for a feedback to the ESC. The feedback prevents that the rotor will go out of sync with the rotating magnetic field. The main advantage of electronic sensors is that even at 0 rpm they detect position.

With a sensorless system there is also a feedback but that is done by the same coils that makes the motor spin. But it is like a dynamo, the lower RPM it spins the lover voltage is produced in the coils. So at low rpm the signal that is send back to the ESC is sometimes hard to detect by the ESC and will act a bit confused what is translated as cogging.

More poles does not matter, only more magnetism in the rotor or a more turns (lower KV) motor can produce a better feedback signal at the lower RPM range.