1. To an otherwise virgin AT firmware from the 1.1.0 SDK I added the following as the first thing in user_init()
wifi_station_set_auto_connect(0)
2. Rebuilt and flashed the new AT binary.
3. Made sure wifi config region of the flash (0x7e000-0x7ffff) was empty of SSID/pass
4. Joined an AP with AT commands
5. Read the wifi config region again.
RESULT: Sure enough, it saves the SSID/pass combo there