yes, you can. You can direct screw OSM on to the concrete floor, but what is the point?why bother? and have fun to put down that many screws down to the concrete.
What I am saying is if you want to put a subfloor to make a difference in terms of getting warmer floor, you need raise it and separate it from the concrete floor. That will take at least that much to do it this way.
More important back to your initial comments on "laying tiles without adding subfloor" - it is perfectly fine for doing it this way.