From my understanding the default is 20ms, but it can be configured in steps of 5ms down to 5ms, subject to the caveats noted in that thread you linked (the 10ms buffer copy, etc.).
I know that PROS has rotation_set_data_rate for this purpose, which in turn calls the SDK function vexDeviceAbsEncDataRateSet. I’m not sure if the VEXCode API has its own implementation or not, @jpearman can answer that.