The problem is that you've selected this before already. Delete what you have, THEN hit the drop-list and you'll get others. Yeah, that's how the console is designed. These are type-down lists, not simply drop lists, so, in short, you have "typed" in an answer already and it filters on that.
As for booting to Linux, it's probably a managed computer - that is, it's already in the console. If a computer is in the console already either because it has booted to WinPE or production in the past, then it wont get either of these two options.