The room thermostat only has 2 settings. It only opens or closes. Everything else is controlled by the heating curve and the preset flow rate. The floats do not necessarily sink completely, but only to the preset flow rate. Presumably, you will notice in the bedroom that when you turn it all the way up, the flow rate is throttled. In contrast, in the bathroom the flow rate is probably unthrottled. You can change the flow rate itself by turning the little wheel on the tubes.
There is somewhere in this forum a thread about how to set everything so that the room thermostats are actually unnecessary. However, this is a lengthy process over weeks/months/years, and I am still not 100% happy with it. For example, my wife found the bedroom too warm. So, just like in the little-used guest room, I reduced the flow rate. But if you forget to close the two doors, of course heat flows out of the other rooms. That means that despite the maximum flow rate, the living room did not reach the desired temperature. So you have to slightly adjust the heating curve. And so you approach it slowly. However, it may be that the settings fit during the transition period but not in winter. So you adjust again slightly.