These are not part of the INDI protocol, but are a convention for naming commonly used properties, so the Thermostat could be given a CONNECTION switch property which it can respond to. I'll try it out - though it may take me a while to get round to it.
Another point to note, as I've been finding a couple of bugs, I've been updating indipydriver, it's now version 1.0.2 available on pypi, so if you're doing any more experimenting it would be worth getting the latest.