because they actually took it down.

It was actually down at the time of that post too. I know because I was using Flat UI in a new project and had to ditch their vector illustrations which were the items in question from this DMCA.

I was not aware from the original post that the project had actually been taken down, and now thanks to pyre's comment I know a bit more about how the DMCA takedown process works. It seems to me that the process is quite vulnerable to Denial-of-service attacks, as demonstrated by the case in question.

They took it down, but you used to get a 404 when you visited the repo. This is the first time that it explicitly says that a DMCA request was executed.

No, I definitely had the DMCA notice when I tried it two days ago.

I remember because I was trying to get it not having heard of the takedown, and it wasn't working, and, after getting to the page, saw the notice.

Why not? Seriously.