For HSP fast track, how is professional work counted in entire fields that are primarily done on a freelance basis?

I am wondering how professional work time is calculated for fields where most work is done on a freelance or individually contracted basis. My husband worked in Hollywood doing beauty work for around 10 years (80-100 hours a week many weeks, so it was a fulltime job) but after the first couple of years, he moved on from being an “in-house” beauty artist to one working on individual contracts with studios. In that industry it’s simply a more freeing and oftentimes better-paying style of work so it isn’t neceesarily seen as a “step down” by any means.

However, I’m wondering if this will not be counted as professional work experience in Japan for fast-track points. For one thing, I feel that some people tend to have acertain view of freelance work that isn’t very positive. Furthermore, I read in one forum that “freelance work doesn’t count for HSP points,” but I’m not sure if that statement is based on a loose understanding of what freelance work might entail (ie the blanket idea that it’s less stable/continuous or less legitimate somehow) of if that’s actually a rule written somewhere.

Does anyone know if this sort of work history is recognized and, if so, how the “proof” of employment is verified? Would he need to get letters from the HR department of the various studios he worked for (probably 5 or so each year over 8 years, plus the 2 initial years he was in-house) or something like that?

Thanks

Note: I am not sure if there’s a difference between a freelancer and an individual contractor, and he may have been the latter if there is.