I think one big difference is that the XIAO BLE uses the second I2C interface with internal CPU connections not brought out to external package pins. The Seeed library code uses Wire1 rather than Wire used in non-Seeed libraries you may come across.
This excellent hardware design means that you can connect any I2C device to the external SDA and SCL pins without havig to worry about I2C address conflicts with the on-board stuff.
Regards,
Dave