According to the ancient list of standard keyboard shortcuts (generally made famous by Microsoft, but used elsewhere before and after), the context menu was Shift+F10 anyway. Plain F10 being the main menu. A context menu key wasn't really needed.

Even the Windows key had the alternative binding Ctrl+Esc for those people who had old keyboards. That's why Ctrl+Shift+Esc called up Task Manager. Related meanings and all that. Arguably though, the Windows key being associated with the space-cadet keyboard's Super functionality was a stroke of genius on the part of Linux adopters. It's also why Alt is often called "Meta".

I'm surprised the context menu key hasn't been called and used as "Hyper", but then there is only one on a modern PC keyboard. There's two of all the others.

(Given the precedent, Alt+F10 ought to be the window manager's "title bar" menu, but the Alt+F# shortcuts are a separate, older, family. Most aren't implemented by default these days, but the famous don't press it without thinking Alt+F4 to close the window is part of it. Alt+Space is what's used instead for the aforementioned menu.)