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.