28 days is 4 weeks, so you don't get fewer or more weekend days arbitrarily. Used very commonly in some industries for financial reporting and also dashboards for software engineers.
If day of the week is important you get more consistent results this way.
I don’t have a particular point of view on this but the people acting like this is weird or some big deal have clearly never spent much time with financial filings. There are much weirder scheduling things than this. Some companies split their reporting quarters up in unbalanced ways for instance.