I got a similar second reply to my original query from someone more technical. He said:
I assume that just means by-room, or by-TRV offset which cancels the effect of their internal calibration. I’m considering adding something like this to the binding already, as most of my rooms are “TRV only”, thus the temps are completely out of whack. An internal offset would allow me to display “more correct” readings at least. I guess this offset would have to also apply to the setpoints in the binding as well.
There are no obvious changes to the JSON, but pulling apart the app shows that the internal have supported an underfloor heating type for a while. I assume it just changes some of the properties in