This seems to be a misunderstanding by the author, a licence doesn't have to be copyleft to be free software. Even the FSF describes the MIT licence as a free software licence (they prefer calling it the Expat licence).

> Expat License (#Expat) > > This is a lax, permissive non-copyleft free software license, compatible with the GNU GPL.

https://directory.fsf.org/wiki/License:Expat

That's not what it says.

It's a table comparing Olive to Vanilla. In the "feature" column there is a row for "Free Software".

It's not saying one is less free than the other. It's saying what you already know: MIT license is not copyleft.