I am not joking.
You might not be joking but you are assuming. Do you have a link to a statement by a site admin that says explicitly that is what it stands for? Otherwise you’re just speculating, and there are other reasons someone would have chosen .ml
besides it standing for that.
.io
is a ccTLD though and is subject to the whims of the British Indian Ocean Territory. They can, for any reason, remove domains. See what recently happened with Mali and.ml
.