Thermostatic Radiator Valve on RTL?

Alright, need some heating advice as well…

I have a small ( around 9 m2) bathroom with floor heating. This is regulated with a RTL valve. But this makes that I am heating the room all day when I only need heating in the evening. I want to be able to shut it off during the day and on in the evening.

Now, I know I could place a extra normal valve in front of the floor heating and put a smart TRV on there.
But my “guy” just was here and said I could just put it on the RTL valve. Now I think there was a (in my eyes) good reason why you shouldn’t do that but can anyone tell me?
Because if that would work, I would put a Aqara E1 (or the new W600) on the RTL that is in a other room and link it to the temperature sensor I have in the bathroom.

What I could maybe think of is that when I do want heating in the TRV on the RTL it just throws the valve wide open and too warm water will go in my floor? It could only work if I was able to tell the valve I want you to be closed or open in setting 4 (this is the setting now with the manual RTL).

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Thanks, but not what I asked.