I feel like you aren't really understanding what a Service-level Agreement actually is in practice. It's not a piece of paper with a specific number of nines and an associated price tag. They can be and often are very complicated documents that take multiple rounds of redlining to arrive at something both parties agree to.

If zero data-retention was non-negotiable for the customer, it's totally possible that the negotiations ended there.

I'm not sure what you're trying to accomplish or unearth beyond what's already been said, which certainly suffices for me.