I found that maximum system clock written in document is133MHz not 266MHz.
I think the reason makes problems not recognizing or not working some Pico board (including compatible board)
It's wired no timing issue with PIO...
There is PicoFlasher binary adjusted system clock. I tested with 16MB NAND, but 4GB eMMC is not tested.
https://github.com/prodeveloper0/PicoFlasher/releases/tag/3.2