And there is another thread in this forum (Wio RP2040 mini - MicroPython firmware) speculating about the author of the micropython port, with a link to github for “IsQianGe” user and project “rp2040-spi”.
The interesting part is that the same author has another project “rp2040_uart_wifi_8285” which uses libat_core.a, and this also describes the ESP-AT command set:
https://docs.espressif.com/projects/esp-at/en/latest/