The following link shows a circuit diagram of the power supply section.
It is not intended to power XIAO from the 3V3 pin. The 3.3V from LDO will conflict with the 3.3V from the external source. It may not be destructive, but you are on your own if you implement it.
‘Charging characteristics of XIAO_nRF52840 and XIAO_ESP32C3 - #2 by msfujino’