I see that type of install all the time and the general rule of thumb is that the concrete should overlap the shingle edge by a few inches. Otherwise , why install it at all. It's not just a detail to look at. It has a fuction and that function is to drain water onto the surface of the shingle or tile. If it's pk to just drain water onto the underlayment, why use tiles at all. UV? well the suns baking the underlayment exposed in those area and will cause it to fail early, yes?
My 2 cents