I don't trust college age guys to groom consistently and sharply. If BYU allows beards, it has to be anything goes otherwise there will always be weeping, wailing, and gnashing of teeth regarding subjective interpretation of what "well groomed facial hair" even means.
Universities without grooming standards show us what that kind of future would look like. Have you ever walked on campus somewhere else and seen the difference? I think BYU campus and culture is served well by the policy.
BYU's grooming standard is not unique. Service academies and the military require it. Professional teams like the Yankees require it. Top LDS leadership appears to require or adhere to it. Missionaries are required to shave and limit sideburns. Heck, JD Vance has made waves as the first President/VP candidate to sport facial hair in over a century.
I recognize it's policy and not doctrinal, and beard cards are available as they should be at BYU.
Also, I was a student at BYU and had to shave and I'm comfortable with that tradition continuing. Not because I want the next generation punished, I certainly never felt punished, but because BYU is special. It's more purpose driven than other universities. It's cleaner. It's different.
I have a short beard myself and have for the past decade.
When I said, "Students? Never," it reflected my sentiment, but was also a bit of a tease as I'm not going to lose sleep over it if they change the policy. I just don't see a compelling reason to.