It's pretty surprising how (AFAIK) macOS still doesn't support adaptive sync displays, that kind of visual polish seems like the kind of thing Apple would jump on.
Does any third-party GPU that Apple uses even support adaptive sync on the Windows side? Because the recent iPads have adaptive sync technology, using a complete Apple stack from GPU hardware to iOS software.
Plenty - higher end Intel Macs use discrete AMD GPUs, and AMD hardware has supported adaptive sync since 2013. It's just not wired up in macOS.
The Intel iGPUs used in lower end Macs don't support adaptive sync though, so maybe it's a case of Apple waiting until they can offer it on the whole stack.