It's nice to see that people are finally agreeing that it unprofessional to expect someone to waste their time when you have no intention of buying the parts from them.
If the person requesting the free information felt that it as a "normal" practice, they would ask for the part number first instead of dead last, almost as if it is an afterthought!
Most of them finish the conversation by saying "Oh by the way, you wouldn't have the part #, would you?