There's a comment at the end of the article explaining that the McDonald's machines are somewhat unique in having a nightly pasteurization process that allows them to go two weeks between cleanings instead of requiring nightly cleaning like other machines.
Listeria is a risk if ice cream machines are not properly maintained. Recent case linked to ice cream machines: https://www.cnn.com/2023/08/20/us/tacoma-milkshake-listeria-deaths/index.html
Not that there are not clearly other issues at play. Just a couple important pieces of what's going on that were not covered in the article itself.