If Rust is widely adopted, and if this commit adds a kilobyte to every language and every library downloaded by everyone, would the fun for the author be worth it?
Really, the scale of efficiency delta between various things used on computers today is vast, and it's hard to say whether something like this "easter egg" is really significant. A few years ago I knew of a linux distro called "slitaz" that was a 30mb ISO, and it had x windows and a minimal window manager and a barebones browser and such.
There are many valid reasons why this should be removed, but binary size is not one of them.
On the other hand, its presence in the current codebase will tend to attract playful tinkerers, which is arguably what it needs in its current stage of development.