My experience with motors is that they are usually specified as Ke = RMS voltage line-to-line / 1000RPM. The reason RMS voltage line-to-line is used, is because it is very easy to measure with a multimeter + doesn't need an oscilloscope.
Kv would be proportional to the reciprocal, and I'd expect it to be RPM / RMS line-to-line voltage.
In your case: 2193RPM / 0.738Vrms l-l = 2972RPM / Vrms,l-l, that's 15% higher than expected. There is bound to be some error in measurement (voltage in scopes is usually 1-2% or so off worstcase), and in part-to-part variation of the motor, but it sounds a little different.
The terminology for brushless, permanent magnet motors is confusing.
If you look in academic/technical literature like IEEE papers, then generally BLDC refers to brushless PM motors that have a trapezoidal back-emf and is driven by a six-step, trapezoidal drive, while PMSM refers to brushless PM motors that have a sinusoidal back-emf and are driven by sinusoidal waveforms. Be aware that brushless motors with a trapezoidal back-emf can be driven by sinusoidal waveforms and vice versa. And also be aware that trapezoidal and sinusoidal back-emf's are ideals and you can never really get either one. Of course, I've also seen IEEE papers that refer to BLAC motors and use other terminology, so this isn't strict across the board.
Industry hasn't really adopted this terminology completely. You often will see companies refer to BLDC motors, as you've already pointed out. And generally by BLDC they mean exactly what the academics mean - a brushless motor with a trapezoidal back-emf. However, I've also seen these referred to DC brushless (DCB) motors, brushless PM (BPM) motors, or even PMSM's.
With what academic literature refers to as PMSM's, I've seen them called PMSM's, brushless AC (BLAC) motors, AC servo motors, brushless servomotor (BLSM) and others.
Some manufacturers may not make a distinction between the 2 because in reality it isn't an either/or thing. You can't make a brushless motor with a perfect trapezoidal back-emf and you can't make one with a perfect sinusoidal back-emf. Your best bet is to talk directly to manufacturers and tell them what you want to do and they will guide you in the right direction.
In reality: Most so called BLDC motors on the market have sinusoidal
back EMF, and can be controlled by the same FOC method as PMSM motor.
But I think they are still BLDC motor, not PMSM.
This may or may not be true. In my experience, BLDC motors do not have sinusoidal back-emf; they are much closer to trapezoidal. Keep in mind that we are talking about the phase back-emf, not the line-to-line back-emf. Sometimes the line-to-line back-emf looks close to sinusoidal while the phase back-emf doesn't.
Best Answer
BLDCs are a type of PM (permanent magnet) synchronous motors, as are AC synchronous motors without brushes. They are very, very, similar.
A BLDC always has armature magnets and not armature windings.
AC synchronous motors have a field winding and can have armature windings or armature magnets. Having armature windings requires brushes though and you asked about brushless so if it is brushless, it must have magnets instead armature windings. That makes the two almost identical, only really differing in ratings and intended usage. (someone correct me if I'm wrong).
For comparison, a brushed DC motor has armature windings, while the field could be either a magnet or winding, which is the opposite which is interesting.
A BLDC motor actually does run on a form of AC when you think about it. It is just not expected to be run straight from an AC source, but a DC source with an inverter in between to synthesize the AC (though you could argue that's just a VFD and VFDs are used with AC motors all the time).
The BLDC motor is more likely to have a trapezoidal BEMF while the AC brushless motor is more likely to have a sinusoidal BEMF to optimize operation with the expected drive waveforms, but not always.