Call it partial support then
Well, they're talking about "officially support", which sounds like it's sufficient.
The MCP they're referring to goes into some detail about what's likely to happen. Older versions of Windows could still be community-supported if someone is willing to do so.
I don't think they always emit code that looks the same, otherwise Windows wouldn't have that awesome compatibility mode in their binaries, where you could run a Win10 binary as if it's a WinXP one.