They would have to fuck up massively for an I/O co-processor to lack single cycle GPIO access which would at least allow driving a 320/2 50% duty-cycle square w

They would have to fuck up massively for an I/O co-processor to lack single cycle GPIO access which would at least allow driving a 320/2 50% duty-cycle square wave, but sustaining that deterministically through priority access to memory and DMA is something else. At 150MHz the RP2350 is able to sustain that bandwidth with hard realtime guarantees allowing it to do things which are hard to impossible on other chips in the same price class e.g. glitchfree 720p video output "in software".