Eight pole 3 phase can be wound with 24 coils. That is 3 single phase 8 coil windings displaced 120 electrical degrees.  Normally that would be done as a 2 layer winding with overlapped coils. If you could imagine this wound in slots then each slot would contain one coil side at the bottom and the other side of another coil would sit on top. Difficult to wind without slots to hold the coil sides in position.

You can wind with 12 coils, each single phase section will now have 4 coils, each under the same polarity. Consequent or phantom poles are formed under the remaining spaces.

This is normally wound with half the coils having dog legs bent at right angles on the end winding, leaving spaces for "straight" coils to fit down in the dog leg bits. This lets the active winding all lie in one layer but the end connections will be thicker and will need to overhang the magnets.

Both schemes are used with radial slotted constructions. The 12 coil method can also be done with slotless radials fairly easily as the coils are pre formed .  Even the 2 layer 24 coil winding can be done with a slotless radial but it is a real challenge.

With axials even with slots the space for overlapping end connections is very limited at the centre and it is a bit of a challenge. When you remove the slots then you start to  run into serious constructional problems.

It so happens that leaving out half the coils of the consequent pole winding will let you produce a 3 phase winding that all sits on one layer with no overlapping. That is the basis of all the 12/9 multiple windings used here.

It could be done as a radial but there would be no point as part of the circumference is not wound and it doesn't make maximum use of materials.

For axials, the entire space can never be used, if the coil legs touch at the centre there will be gaps between them on the outside. This wasted space and the difficulty of dealing with overlapped ends at the centre makes the single layer winding attractive. By playing with the pole spacing it is possible to reduce the unwound portion to under 25% and considering the increase of resistance from the extra wire needed to overlap the ends you arrive at a situation where this single layer winding will be as good or better than the difficult to wind overlapped coil version.

If you are in an area where corrosion is an issue and you want to pot the magnets then the overlapped coil winding presents real problems and you will have to stop the potting beyond the magnets on the inside and outside for the bent coil ends to lie in.

All of this adds up to the fact that with an axial design it is never worth the struggle to use other than a single layer winding. So unless you want to sweat blood for no reward your best option is 6 coils.