I know that some applications have forms with questions and checkboxes for referees to fill out in addition to uploading a letter. Do these questions ever differ depending on whether the applicant has selected an interest in experimental v.s. theoretical physics? For example "In your opinion, how does the applicant's potential in experimental physics compare to those of other students?" as opposed to the same question with experimental replaced by theoretical.
In general, do the letter writers who are added have the ability to see
1) whether the applicant has selected a preference for experimental v.s. theoretical physics?
2) any other information about the application?
In particular, I'm interested in whether this is the case as top-tier schools such as Harvard, Princeton, MIT, Caltech, and Stanford.