I haven't done an exhaustive study on the rate of loss of hair from either the head, beard, arm, etc. but the issues of hair shedding onto packaging or into other products is more than just physical it is also microbiological. When employees eat do they wash their beard, goatee, soul patch? No. They, should, wash their hands but other areas of potential contamination still exist. Food quality is about mitigating potential risks and hair is well known to be one of them.
Like I said in another thread I worked in a food product with people that have an ethnic origin known for having long thick arm hair and it was pointed out that there was no requirement for sleeves. How easy is it to lose arm hair v/s facial/top of head hair? I don't know why arm hair, many times, is exempted I just know it is. In some jobs when you are dumping bags of ingredients in there are requirements for sleeves such as a yogurt plant I worked at. When people were batching or dumping ingredients into a hopper they had to wear sleeves. Some places require it some don't.
However you can't just say "I got the hair out I'm good" it's not, to me, that black and white.