Hmm, I may be old fashioned and I do admit not much experience, but every casino (talking about normal ones as well, not just crypto) I played on (like 5-10), never had free promo money that I could just withdraw without anything *scratches his head, thinking*
weird, I had plenty of casinos that offer no strings attached, no deposit bonuses
that you can win from and withdraw after, easy and no hassle
of course, many would not do it but that was just free money and you would just forget that casino's name and web addy after that

in many cases free spins or bonuses come with wagered requirements
but you can wager using that bonus, this is the big difference!
if you are lucky you can wager the free spins you got and withdraw without depositing your own money
here, it is impossible, hence it cannot be positioned as a no deposit bonus