Win32 is kind of legacy.
UWP is what was WinRT on Windows 8, they have just been improving it all these years.
Of course they have access to full DirectX 11 and 12.
All new APIs are UWP based, and with they learned with the Desktop Bridge for Win32, they changed their strategy and are now merging UWP and Wi32 into a single container/store model.
Some of the talks related with it were done at MSBUILD 2018, check MSIX, .NET Core 3.0 roadmap, XAML Islands, XAML Direct.
If they don't change direction, in a couple of Windows releases they will be merged, with UWP continuously taking over Win32, like Win32 did before to Win16.
As for Apple, I can quickly refer to Object Pascal, Quickdraw 3D, JavaBridge, Quickdraw Java APIs, A/UX, Dylan, Newton, MCL, Hypercard....