Fair enough. I am one of those few sellers and I tend to assume it's more commonplace than it is.
In any case, I don't really understand the desire for instant disbursements. Certainly you eliminate the risk of Amazon carrying a larger balance than necessary, and in rare cash crunch situations it may rescue the day... But beyond that, why is it so desireable?
For most businesses at scale, cash flow is a gating factor for growth and profitability. This is why businesses always try to get cash on delivery, but pay their vendors Net 60.
This applies to very few sellers.