The answer is yes and no. There are certain colleges that never seem to lose many kids to the draft. Stanford, Vanderbilt, Virginia, to name a few. So if the kid is a Stanford recruit it is generally thought that kid is going to school.
However, more important is the signability scouts do on each prospect they are interested in. They don't just forget about a kid because he happened to commit to a certain college. They go through with signability and determine the players interest in signing a pro contract rather than attending college.
The major reason for all the interest is the players ability and projection. They (the scout) understand the history with certain schools, but they still have to find out.
So bottom line... The history tells us Stanford, Vanderbilt, Virginia, etc., commits tend to end up going to college, more so than many other colleges. But first round ability is first round ability and it is never ignored because of someone's college choice.
It is when scouts sit down with the player and his family and start asking signability questions that the college choice might come into play. If that doesn't happen, the player that thinks he would have been drafted had he committed to a different college is just fooling himself. It just means they never considered that player as a potential good draft pick. They want to know what the top players want to do. They want to have an idea of what it will take to sign them. It is a big part of the scouts job! He can't just assume that the college choice tells him that the player is likely to sign or go to school.