Apologies for the delayed response. What you're describing is not novel to crypto. Citadel is a wholesaler, but plenty of other participants quote firm bid/offer prices on real exchanges (where the wholesaler sends their exhaust). In the US equity space there is RegNMS that seeks to model the marketplace as a single entity, so it's a bad example; but there are plenty of other examples of non-fungible products that trade more similarly to the crypto markets. For example, there are gold markets across the world with slightly different quality standards, units of measurement, delivery standards (or cash settlement rules), expiration dates, etc.