“principals lower themselves to the level of “friend” and discuss with bochurim things that are not on their level to discuss”
I don’t think the issue here is “shmoozing” with students, it is garnering information from them. The bottom line is that friends know much more about each other than teachers and principals know about them, and they are freer about sharing honest info. Obviously the principal will take into consideration the maturity of the source of his information when determining its reliability.