Yes, when there is a motion (or a human 'presence' in the mmWave radar detection area) the child device 'motion' attribute should change to 'active'. This is the standard HE Motion capability, you can use it in automations, dashboards, etc..
I suppose you have the Meross mobile app? All the configuration options for MS605 are there....
Compare the three motion zones states in the Meross app - the three motion sensors in Hubitat should reflect the active/inactive (occupied/unoccupied) state the same way as in the app.