After a careful search of BSP 2.2.0, I found a loop function already prepared to avoid bricking.
There is no need to call any particular function, just set PC0 = LOW and reset to enter the loop and enable upload.
Care should be taken when using PC0 as its own I/O.
See below.
\Arduino15\packages\SiliconLabs\hardware\silabs\2.2.0\libraries\ArduinoLowPower\src\ArduinoLowPower.cpp:L240 escape_hatch()
\Arduino15\packages\SiliconLabs\hardware\silabs\2.2.0\variants\xiao_mg24\pins_arduino.h:L114