Best not to trust pseudoscientists but rather actually sun/skin specialists such as oncologists or infectious disease doctors.
I’d like to point out something the pseudoscientist (the guy you said is an expert didn’t know) sunlight is a good source of D3, which can be obtained for animal sources. You still need D2 both are needed for adequate absorption of calcium in the body. Another important factor is that too much D3 from sunlight, or other resources for example you ate animal resources d3 and had a ton of sunlight & took vitamin d pills everyday for a while can lead to signs of vitamin toxicity: nausea, vomiting, frequent urination, pancreatitis,  and many other side effects. As always, all things in moderation :) 

nostr:note1v3yphfdx49u0ytzupuvr0u67ae834755jywwd693zvgjln9uwjpsuagz5f