It depends in the requirements of HP committee. A small number don’t require any supporting LOEs from s student’s professors; most do require at least 2 or 3 LOE from a students professors.
But for example, if a med school requires a LOE from a non-science professor (very common), but the HP does not ask the students to provide a LOE from a non-science professor and doesn’t not include it in their HP committee packet, then a student is not expected to provide an additional non-science letter for the med school. The HP letter will suffice.
Does the committee tell you which of the 4 categories you fall under? I presume they must tell the student if they’re in #4, but do they specify if you’re in 1-3?
A student will usually be told if they fall into category #3 or #4, but usually won’t be told if they are in category #1 or #2 since letters are confidential and not shared with the students. Student typically sign a waiver relinquishing their rights to see the committee letter. (Having a non-confidential letter is a red flag to adcomms and signals the contents of the letter may not be completely forthright and trustworthy.)
It sounds like schools that use committees might have a less collaborative culture since students are fighting to be in group #1.
This is really dependent of the culture of the particular school.
Students will know their GPA and how other students have done in the same classes they took, of course, but the other items that go into the HP’s consideration–MCAT score, strength of professor evaluations, quality & durations of ECs, HP mock interview performance-- those other students won’t know. In fact, the student won’t know the contents of their professor evaluations (because students are required to waive their right to see those), or how the committee perceives a student’s ECs.
So a particular student won’t know exactly how they stack up compared to other students at their school.
Plus there’s no rule that says most student can’t go into the highly recommended pile…