at BYU as well as numerous other universities. I have interviewed hundreds of job applicants from dozens of universities over the years, both MBAs and undergrads. A few thoughts on your post:
1. As a recruiter, I couldn't care less whether or not someone I'm interviewing has a beard or other facial hair, as long as it looks reasonably well groomed. I recognize that there are still some recruiters out there who probably do care, but in my experience they are few and very close to retirement.
2. Even if this is an issue for some recruiters, being clean-shaven or well-groomed means more when it isn't forced. Most people I interview present themselves well in terms of physical appearance, which includes shaving or grooming their facial hair. At most schools, this shows some level of maturity and initiative that separates them from the average college kid. At BYU, being clean-shaven is meaningless because of the school's rules, and recruiters know this.
3. Only a small minority of college kids are interviewing for professional jobs at any point in time, so it doesn't makes sense to make a rule for the entire student body based on what may be good for interviewees. This is not the reason this rule is in place at BYU.