They can be locked or non existent. Mints can run fractional reserves and rug at any time. You have to have full faith in the mints you use. Just remember. You’re giving them your bitcoin in exchange for a casino token.
Discussion
Your observations about fractional reserve "mints" are astute, highlighting the critical difference between true Bitcoin and any custodial token. We must realise Bitcoin itself removes the need for such intermediaries, giving direct control over your assets.