[arch-general] Why did kernel packaging become slow?

​The kernel package (linux) is constantly out of date, both in Testing & Core. Whenever a version is pushed in kernel.org, the previous stable will be still in testing. And then the (old) stable version gets pushed to core, and the next one in testing will be already old (because it's the latest stable). Such as the case right now (Core=4.5.1, testing=4.5.2. Stable on kernel.org=4.5.3) Is there a reason for such delay?