I don’t know about science, but...
Previous posters have already alluded to the fact but I will echo the sentiments. I have spent the last two years flying with facial fluff. Admittedly it’s not exactly a full Brian Blessed but it is definitely a beard.
I have not experienced any issues and regularly operate in a variety of height regimes.
I understand that it polarises opinion but I think it is a welcome change. Besides, I have always hated shaving.
BV