I asked to see the datasheet of the $32 motor and this is what I received:

The phase resistance is 1 / 2 of the terminal resistance (the resistance between two terminals, I presume), so it's 9 ohms. 

At this point in time, I'm also asking around for the rotor magnet and it's sounding like 1 pole pair is much easier to make than 2 pole pair:

It seems that Sinbad Motors has also gone with the 1 pole pair approach.

Additionally, the STSPIN32G4 is only a gate driver. Basically, I'd need to provide 6 MOSFETS to actually drive the motor, and that's a lot of traces:

It seems that the TLE9879 is similar in this regard:

I thought that all that would be integrated, like this HT32F65C40F:

Thus, it does seem that I'll just stick with the original controller plan of using tSPI, which would only need 3 pins since it'll likely be the only SPI chip on the PCB.