I posted this in a similar thread.
I don't think you understand the actual process. Apple submits its updates for testing and approval to each carrier. Once it gets approval from the carriers it then pushes the updates. It's all done in the background; users never see, the "sausage being made." Also, Apple does not send out monthly updates. If only does yearly OS version updates, and only pushes of "dot" updates when it finds a major bug. Which usually happens after it pushes out a version update.
Finally, Apple only supports one OS version (the latest) and it only has a few devices. When a new version of iOS is released, it stops sending out updates for earlier versions. The carriers only have to deal with Apple for ALL iOS devices. Where as Android is on a variety of devices made by a variety of OEMs. The carriers have to deal with multiple versions of Android made by several different OEMs. The OEMs, themselves have to support several devices as well as different versions of Android.