PC desktop chips have 128 bit busses to right ? From what I know theoretical maximum memory bandwidth of chips is less than 100gbps - which is less than like base M5/M4 chips.

So no matter how much compute you stuff in there it's going to be shit for AI ?

PC architecture is not adapting to AI workloads at all, and no signs of that changing in years to come. I would not be surprised if your phone was more capable of running AI models than an average desktop - especially given gpu pricing.