What is the terminology of, and relationship between, these two characteristics of gimbal motors?
Both the jerkiness and positional accuracy are a result of torque ripple and how the PID control loop interacts with it.  In other words, they're different manifestations of the same thing.
Torque ripple is itself is a result of something called cogging torque.
Cogging is easy to identify: rotate any permanent magnet motor's shaft (whether it be brushed or brushless, it doesn't matter) by hand, and you'll feel that it does not rotate smoothly - instead there is a noticeable variation in the torque needed to rotate the shaft, and certain positions the shaft will prefer to be in, even returning to that position if moved a little off of it.  Or snapping into a new position if moved further still.
You can think of them as magnetic detents.  The motor's construction features permanent magnets and a series of magnetic cores that windings are wrapped around, with gaps in between, known as 'slots'.  These magnetic cores serve to increase the strength of the magnetic field the windings can generate, but as a result, the magnets are going to be naturally pulled by these cores as, by necessity, the cores are made from ferromagnetic material.  The magnets are simply called 'poles'.
Additionally, when the windings are energized, this results in the distance to the highest field strength generated by these poles and the motor's permanent magnets varies with the rotor position.  As a result, the torque the motor generates varies as the magnets go into and out of alignment with the poles, resulting in a ripple if you were to graph the motor's torque vs. rotor position.  Hence, 'torque ripple'.  And when loaded, variation in torque will also result in variation in speed.  When this variation in speed is low frequency and large, we perceive it as 'jerkiness' in the motor's movement.
There is no hard or fast measurement that lets you know what the cogging torque will be.  Variations in construction and various other techniques that are rarely, if ever, mentioned in any motor data sheets can play a large role in determining how much or little cogging torque and torque ripple a motor will have.  The single largest factor is simply the type of magnets used in the motor construction.
When comparing motors of otherwise similar construction, a higher number of poles will correspond to lower cogging torque and torque ripple amplitude.  However, they will also result in a higher frequency ripple.
The magnitude of the cogging torque is not what determines smoothness of operation in the context of a gimbal motor.  Yes, more poles means smoother rotation in other applications, but gimbal motors are unique in that they are controlled by PID loops designed to track a position.  Large amplitudes in torque ripple are easily compensated for if they are gradual enough for effective tuning of the PID loop.
This means that it is the frequency of the torque ripple (and as a result, the rate of change) that is far more important in gimbal motor performance.  It is much more important that the PID loop be able to control the motor, than it is for the motor to rotate smoothly when used in a simple 'dumb' (non-positional control) application.  For this reason, lower number of poles are better for gimbal motors.  Higher number of poles might seem like they'd be better, but they severely limit how well tuned any PID loop could possibly be for that motor, and at that point, the only way to avoid the jerkiness you've described (both in movement and positional accuracy) is by using a weaker PID tuning - which results in a lot of lag and performance that, while smooth, feels 'drunk' and is unable to react quickly.
Fewer poles will result in smoother gimbal motor operation and higher positional accuracy.  It may be counterintuitive, but it is true.  For this reason, most commercial gimbals have gimbal motors with as few as 9 poles, and certainly not 22 poles or more.  Definitely avoid any motors with more than 12 poles if you can.
Of course, the ideal is to use a slotless and coreless gimbal motor, which does not have  any cogging torque or torque ripple at all.  This allows the best tuning of the PID loop.  Unfortunately, these motors are also by far the most expensive and can be difficult to source.
If limited to cored motors, ones that use a ferrite ring in their construction rather than rare earth magnets with a low number of poles will give the best performance at reasonable cost.  The problem is it can be very difficult to determine if a given motor uses this construction or not as most manufacturers don't mention such details.  You'd have to physically disassemble the motor and look inside (if it has a dark grey ferrite ring inside, that's all you need to see).