In the case of very low demand, where I agree the boiler might have to cycle even with opentherm, isn't it better to cycle with a low setpoint than with the boiler going full blast?

Not just from a savings point of view - I'm actually thinking more in terms of control and comfort. Rooms with oscillating temps, for example. I used to see that a lot when I used TPI, but not at all now I've gone to Opentherm.