Atomic swaps don't depend on a provider or platform. Atomic swaps are direct between the two parties involved, no need for a trusted 3rd party.

If Alice has sBTC and wants to atomic swap with Bob for his BTC, they can do so instantaneously (or at least within Bitcoin confirmation times). Alice and Bob do not need to trust each other. Both are trusting Bitcoin and sBitcoin's consensus, but thats already the case since they intend to use Bitcoin and sBitcoin

 The bitcoin side of the swap cannot be reversed without a 51% attack on Bitcoin. The sBTC side cannot be reversed without a 51% attack on the side chain. These attack risks can be accommodated by waiting appropriate confirmation times on each chain before finalizing the swap.