I believe this blog has at least part of the answer to your question.
Brushless gimbal motor vs. Brushless Motor vs. Servo
A user here described the comparison as:
A brushless gimbal motor is a regular brushless motor but wound for very low speed (ie lots of turns of thin wire) and many do indeed have more poles.
Another post continues:
They are both low and high speed at the same time. Low speed, in that they never actually
complete a full 360 rotation so you wouldn't normally think of measuring their speed in rpm,
but high speed in that they need to respond instantly to sometimes very rapid changes
in direction as the aircraft may be getting shook by vibrations and turbulence.
That means they're meant to be light and fast, not powerful and slow.
These motors are not meant to carry any kind of continuous load.
Generally, I think it can be said that a brushless gimbal motor is one specifically wound to be used in fine control applications. A brushless motor on the other hand might be considered more of a load bearing motor.
That being said, most brushless gimbal motors are used in applications that could otherwise be filled by servo motors: finely controlled applications.
I hope this helps.