Sometimes it is difficult for a h.s. player to know whether he can "honestly compete for a top 25 spot on the roster." He may be "the bomb" on his high school and select teams, only to discover that he is in the middle of the pack (or even lower) when he is comparing himself to his college teammates.
On the other hand, a good college recruting coordinator should have a pretty good handle on how the h.s. player will stack up against his future college teammates. I don't believe it is right for college coaches to bring in a bunch of extra players, knowing they will have to cut many after the fall.
H.S. recruits should ask LOTS of questions going in. How many players at my position have you already recruited? How many do you plan to recruit after me? How do I stack up against current college players who play my position?
Even then, some colleges may not be totally honest with their answers. Colleges can and do publish the names of their NLI signees, and recruits can quickly scan that list once it has been published. But the NCAA prohibits college programs from publishing the names of their recruited walk-ons, so it is sometimes difficult to know just how many players are actually being brought on.