What's the usage of V_ref?
Could you verify that all SPI pins are signaling at 1.8V, please?
Which pin is supplying the 1.8V input?
Have you decided which rail is GND yet?
Edit-1: Or are both rails supplying the internal voltage, and the only GND is the central pad?
Edit-2: I hope both rails aren't V_internal, since that would force either a 4-layer board, or high inductance breaks in either the cooling GND plane or the V_internal plane. There is a reason that prior chips didn't use a plugged-tunnel approach to pinout...
P.S: a link to the github location of these specs would fulfill one of your previous promises....

Thanks!