I thought this was pretty fascinating. I went to the barber and selected Clean Shaven for my beard. As I was doing my quests and adventures, I noticed Geralt’s has a full beard. Didn’t I select to be clean shaven? Well turns out, Geralt’s beard grows over time!
It doesn’t seem to automatically grow if you just spam meditate though. I think from doing a series of quests and waypointing,etc.