What third party app are you running offline? By third party I mean something not built into the OS like a notes app, file manager or camera app.

Fitness and calorie tracker, ebook reader, notes app (Android doesn't have a good notes app built into the OS), music player app for music I have locally on my phone, and an app that configures my bluetooth headphones.

Gadgetbridge is running great locally without dumping your most intimate data into a vendor cloud.

running meta's social media apps offline doesn't seem particular compelling.

I can't tell if you are deliberately being obtuse but they are talking about apps overall and not Meta's apps. Many apps use Facebooks SDK because of the Facebook Pixel for tracking and advertisement. Web apps don't prevent that and again, cannot be easily run offline so I'll stick with my native apps.