He is a Scientologist.
Yeah I looked him up too. My brother watched his videos and I wasn't overly impressed, and the Scientologist thing is not a positive sign to me. Not to say he doesn't say some good things as well. But there's lots of pseudoscience in his vids, theories are fine but you gotta be critical.
Regarding the D dosage thing, they recommend blood tests if taking over 5K a day and I'm sure it's a good idea but for me that's too complicated to get done regularly. I got these 17K mega-dose caps (one every 2 weeks according to bottle) and take a couple every few days, kinda stupid way to take it tbh. Someone on a steroid forum said a bodybuilder should take 30K a day with vitamin K because enhanced bodybuilders "go through a lot of it." Another said he needed 30K a day to get to high normal, but then other said they have good levels at 4K. Too much is of course very bad, Phil Hernon claimed lots of bodybuilders would get kidney failure due to the vitamin D craze, but he's no doctor obviously, just a bb, but he had kidney failure, doubtfully vitamin D had anything to do with it though. Just relaying what he claimed. Looking at supps, I saw some 200K caps sold lol, one cap to be taken every 2 months. Now I'm again thinking my caps don't have the vitamin K, there's just too much to be mindful of to remember everything

I've seen it stated that 10K is what the body can produce in a day if out in the sun some, so 10K "should" be ok to take.
If low I'm sure it could be pretty anabolic to raise levels, and there are some studies showing increased strength and gains in lifters with D supps. Besides the immune support and everything else. My main reason for taking it is the immune part, with my history with swine flu and covid. I take Zink too with this in mind, if noticing first signs of flu I take a big dose immediately, about 100mg elemental, supposedly the only proven way to limit the duration of illness. Zink is also toxic if using to excess.