All Apple hardware has Windows drivers thanks to Boot Camp. So presumably those drivers will display function keys.
Linux and the like will be interesting, though.
I think it's a good possibility that for operation systems, and even applications that don't take advantage of the bar that there's a default that behaves like the existing key row.
They don't want co-installed operating systems. Just like they don't want wired headphones.
I was just thinking that earlier today when I was enabling installing apps from "anywhere", which is now a hidden option that can only be enabled from the command line.
You can still install apps from anywhere. The hidden option allows you to bypass gatekeeper, which IMHO is a fantastic security feature that stops people from installing potential malware or unsigned binaries.
Right click the app and choose "Open". No need to turn it on globally.