Nope, even stock, gold, real estate didn't qualify as proof of funds, so I'm not surprising to see Bitcoin didn't qualify too. However, I'm shocked that your friends didn't have emergency funds, no matter how big your trust in investment, you need emergency funds in order to prevent you to sell your investment at loss.
The proof of funds isn't big because your friend only apply for tourist visa, not working or skill visa.
Yeah this would be different for El Salvador since they treat Bitcoin is same to fiat.
It would be yes if it's El Salvador as you have said in your post since it is the first country to accept Bitcoin as their legal tender. Op's friend should sell some of his investment up to the amount required. That way, op's friend still have some investment and also have emergency funds. I wonder what this person is doing now after op posted this if he decided to sell portion of his investment or not.