... but I still can’t remember feeling the tiles at about 5°... not even at 20° outdoor temperature.
Tiles made of ceramic and the like are cold! Yes! Also to the touch! But whether it’s a heat pump or gas... why should the heating turn on when the thermostats are set to 20 degrees and the outdoor temperature is 20 degrees?
Wood is warmer, and is often chosen specifically because of the perceived warmth underfoot, just like cork and linoleum.
In return, ceramic heats more consistently and has a "faster" efficiency, if you can even say that about underfloor heating.
If you want to have warmer feet, I would simply set 25 degrees in the bathroom and experiment a bit.
Whether that is a disadvantage with a heat pump, I can’t say because I have never dealt with it.