I second this. No shortcut to search history, just start typing and hit up. Instead of ctrl-e or whatever it is, it has the same "move by 1 word" shortcut as literally everything else on the computer. The pre-made prompt configurations that you can browse (with preview!) in a web browser is nice too. ZSH doesn't compare imo.
Interestingly, none of the two Bash versions in the comments are equivalent to your code, which kind of prove your point with Bash being tricky. `while sleep 1` means the script will sleep once before running `df`, while it should only sleep after. The other command also won't work because it's missing colons between commands.
I second the voices, one downvoted but none really addressed, wondering why this is manifestly an improvement over the bash equivalent.
I certainly don't demand that everything in Fish be an improvement over everything in bash for Fish to nonetheless be superior... but this was presented specifically as an example of how Fish is great, and I could just as well say "Guess what this does" of the obvious bash equivalent: