Sure it can provide an SLA. The code is the SLA. And is available for all to examine. Via opensource. And governance allows the community to change terms/accept code... moving forward.
It's not _likely_, as that would negate the usefulness of the whole system if it became an issue, and therefore negate the cash flow into the system.
Ultimately what's keeping the storage providers honest, whether they're centralized or decentralized, is that their future profit stream is based on their current behavior, and they presumably care about future profits. Code and SLAs ain't nothing but words.
Disclaimer: I have no idea how these systems currently work.
So the code shows file, all my proof of storage is correct and users are hosed. There’s no “proof of bandwidth” (yet)