Except that apparently under certain circumstances it doesn't persist data, which was the author's point.
Personally I wouldn't be upset about a limitation like the one described as much as I would be upset about the database not logging an error when it discards the data. Logs are a primary way you figure out what's wrong when your application isn't behaving as expected. If you open the logs and see a bunch of "32-bit capabilities exceeded, please buy a real computer" messages, you learn what the problem is. If the database error logs are empty, that implies that everything is working fine, when in this case it clearly isn't.
Almost all of the complaints against MongoDB are down to assumptions and lack of understanding about the database.