Disclaimer: I work at Microsoft but not on Windows or Edge. I also don’t have a full understanding about Web Environment Integrity, but am basing this off what I understand. This article states my opinions, as opposed to that of my employer.
If you haven’t been under a rock, you may have heard about Google’s evil Web Environment Integrity “proposal”. Supposedly, this is to make sure a browser environemnt can be “trusted”, but it seems Google wants this so they can kill ad blockers.