Of course, while the central app service has indeed down for a period, some of them had logged out of their apps.
And, according to the article, they actually COULD have used their cars. From the article
"While Tesla’s app helps you unlock the car, you can still use a key card, an option key fob, or the app without needing to connect to the internet. But some people who didn’t have the key card or the fob, and were logged out of the app, had to wait at the time of reporting."