I don't think every app comes with a clear label attached, but I think most people could decide which apps are the product and which apps are just a feature for the product. For argument's sake, I'll claim the core distinction to be if the only realistic alternative to use a product is through an app on another platform or through a web browser, then the app is the core product and not just a supporting feature. The product can live on servers, but if it weren't for the app then the servers wouldn't matter.
I can still drive a Tesla without the app. It's clear that the core product is car, not the app. Some people may have bought it because of a defining feature, but you are not paying $80k for Summon mode. You are paying $80k for a car that has Summon mode.
Wells Fargo offers almost all of their functionality through physical branches and ATMs. Having an app is just a feature, a bank account is clearly not an app.
I cannot use Netflix without an app or browser on my TV, phone, tablet, or computer. There are movies stored on servers, but I'm not paying $15/month unless I can watch movies. That means Netflix's core product is an app and per Apple's rules they should offer in-app purchases.
WeWork is a little harder for me. They are a real estate company but I'm not sure you could call WeWork and get a workspace over the phone nor could you do it in person (you can call a landlord directly, but that is not WeWork's product). I think their core product is that you can book a space online or with an app. I think they need to have in-app signup and purchases.
Github is the most gray one for me- once setup, I use it mostly through the command line. I could claim that the core product is not an app, but I don't honestly believe that. I use a significant part of GitHub's feature set through the browser (discovering repositories, clicking through links to read about a package before cloning it).