ThermostatSetpoint:DualSetpoint is the only thermostat type that OpenStudio uses: if you want a Single Heating thermostat you must put a cooling schedule with a very high setpoint, or it'll get deleted on forward translation.

ThermostatSetpoint:DualSetpoint will be reverse translated. See ReverseTranslateThermostatSetpointDualSetpoint.cpp and where it's called in ReverseTranslator.cpp.

I can't seem to see any other reverse translators for thermostat objects.

Side note:

I'll let the OS team comment as to why there's no reverse translators for these other objects (funding?!).

But I just want to say that this wouldn't be very hard to do though, and it would be a nice addition for all users out there, maybe you could rise up to the challenge?

Even if you don't really know C++, my recent experience with adding objects to OpenStudio suggests that this is a lot more intimidating than complicated. These specific reverse translators would surely be pretty simple to add by just reading the developer documentation (especially this) and replicating patterns you see in similar files.

And if you don't want to do it yourself, you could always post it as a feature request on User Voice.