It's only being made important in order to obfuscate the process.
Imagine I took a hose, and put a sprinkler on one end and left that in my yard; then attached the other end to the spigot of my neighbor's house.
My neighbor comes to me to complain, "You're stealing my water!"
"Oh, but I've tangled the hose so much that even I can't prove where the water is coming from! Furthermore, I've gotten permission from our other neighbor Dave, and you can plainly see that I'm using his water. Maybe some of yours has been mixed in, but the courts have deemed that 'fair use'. After all, I can be responsible for tracking down where every drop of water comes from!"
"You attached the hose right here to my spigot! Water is flowing out of my house into your hose!"
"As I stated before, no one - not even I - can prove whose water is flowing through my hose. You can't compel me to untangle my hoses!"
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This situation is obvious. I have left my hose tangled in order to dodge responsibility for taking your water. When someone does this with money, it's called "laundering". The only difference here is that it's an asset (copyrighted source code) and not a currency (dollars) being laundered.
It's further complicated by the fact that you can't "take away" source code. But the entire premise of copyright is to pretend that you can: to violate copyright is to use the assets created by someone else, thereby ignoring their arbitrary monopoly.
Fair use allows us to accidentally or incidentally use copyrighted works, but that clearly isn't what Microsoft has done. They are just using all the code they can get their hands on, and laundering it through ML.