It obviously uses "a program, a hack, or configuration" (taking these from the original reply), just that they are written and pre-installed by Apple, and work seamlessly.
But from the end-user perspective it doesn't really. Nobody consciously sets the universal clipboard up, it comes as part of the cohesive whole of the Apple ecosystem. That's my point. Whether or not you want to dive deep into nerdland of if it's a program or not is besides the point, because for the end-user none of it matters, and that's why the vertical integration is nice.
Probably true. The whole vertical integration does rub me the wrong way though, it's just uncomfortable to have one company own so much of my personal computing infrastructure, especially one that is so unfriendly to "tinkerers" like me.