What's the difference between the thermostat for electric baseboard and in-floor heater

If it's a low voltage thermostat, then probably, if it has terminals for sensors. If it's electric baseboard, then no.
There are many more design criteria needed than to just put a loop in. How are you controlling the supply water temperature, for starters.
How does one thermostat save $700-$800 dollars?

The OP stated in another thread he has 5 floor mats. So @ $150 each he gets 700-800 I suppose. Electric floor mat controls typically use floor sensors. Most or all can use room temperature if one digs into the menu. So I suppose a line voltage Tsat would be OK if the circuit is GFI protected.

Quote from OP: "Beside the fact that in floor heating has the floor sensor, is there any other differences? i am installing a in floor heating system that has a maximum temperature of 85F which is perfect for my vinyl floorings. Can I use the baseboard thermostat since they cost half as much as the in floor thermostat, and it can save me $700-800? what are considerations I should be aware of to make the decision?"

Answer: Yes there is a big difference: GFI protection. Don't discount this. You were talking about vinyl floors in the other thread. Very easy to cut through accidentally which could cause a short circuit but might not trip a regular circuit breaker. You can get GFI protection with a GFI outlet in front of the Tstat (wired correctly) or a GFI circuit breaker.