At least on my laptop, the grub menu has a list of options plus a sentence saying you can click the arrow keys to choose an item. It also says you can click "e"

At least on my laptop, the grub menu has a list of options plus a sentence saying you can click the arrow keys to choose an item. It also says you can click "e" to edit one of the entries there. Once you've clicked a key there, the timer to automatically boot stops and you can take your time. On my laptop the default configuration automatically boots too fast to read all of the sentence there. That's bad, but the tradeoff is I wait less time for my system to boot for all the times I don't need to reconfigure the boot. That's what I mean by self-documenting, which the "boot>" example you gave is not. (Nor do I see any documentation about why it's not self-documenting.)