My understanding is the earlier versions of postgres required more expensive patching to support their proprietary storage layer. Some of the common hooks have

My understanding is the earlier versions of postgres required more expensive patching to support their proprietary storage layer. Some of the common hooks have since been upstreamed (whether aws gets any credit or if it was part of other work I couldn't say), but in theory aws doesn't have to do as much work to support new versions as they used to.