I haven’t experienced it live yet, but maybe you could just buy a tile, warm it up to 25° with a hairdryer and put it on your stomach. The ultimate tile test.
What’s that supposed to achieve? Are you walking on your stomach?
And regarding the bathroom and the positioning of the objects. Good planners already take that into account when designing the floor plan. It makes no sense to give the bathroom 4 walls and x sqm and then awkwardly squeeze the objects in afterwards.
What is that supposed to achieve? Are you crawling on your stomach?
Aren't you? No, but children lie on their stomachs when they play in the living room. I would indeed not consider adults' feet to be critical with underfloor heating.