The license wasn't changed. But yes, generally you can make changes to MIT code that aren't released under the MIT license.
> It's definitely the case that at a given snapshot of the repository which has copyrighted code owned by someone else the copyright notice has to be there at that same revision.
This isn't in the license. Where is this laid out?
> It's definitely the case that at a given snapshot of the repository which has copyrighted code owned by someone else the copyright notice has to be there at that same revision.
This isn't in the license. Where is this laid out?