That is what I thought - the T6 appears to just switch the boiler in and out - simple and crude on-off control not modulating the burner. Using one of those stats, you may as well hook up the outside temperature sensor to modulate the burner, as Intergas boilers work with either the outside weather compensation or the Opentherm internal room thermostat - not both. That means buying a non-RF Intergas combi (which are cheaper) if using the T6 - may as well use the cheaper and very good Heatmiser RF stat and save again.
The Intergas RF manual does not mention the Honeywell T6 but mentions other compatible Opentherm RF stats. That does not mean much as the manual could be out of date as new stats arrive on the market.y to the stat
EDIT: Found that the T6R does do Opentherm via RF, but needs a power supply to the stat, so not wireless really. The T6R appears to be a roomstat you put on the sideboard.
Oh dear, you can't have OpenTherm over RF and the low modulation control profile of the T6 is the best on the market right now but you keep on googling you way into a deeper hole