The majority of them are companion apps for physical products/memberships for which the rules around in-app purchases do not apply: Tesla, Soho House, Wells Fargo, Blue Cross / Blue Shield, WeWork.
Github has a free tier and doesn't require a paying membership to use.
Netflix is a digital content app for which there is a specific exemption under rule 3.1.3(a).
Bloomberg and Salesforce might also fall under the 3.1.3(a) exemption for "access to professional databases", I'm not sure.
App Store Connect is their own app. Apple's apps have always been able to use private APIs and do other things the rest of us can't.
The only other app in this list that is actually similar to Hey in terms of product type and monetization is Fastmail. (And it looks like Fastmail was recently asked to add IAP to their app as well.)
The rules around in-app purchases have been well known for a long time (by iOS devs at least, clearly not by the general public or even tech people).
Releasing an app that does not follow the rules and then publicly complaining when it is inevitably rejected is starting to seem more like a guerrilla marketing tactic more than anything else. (And a clever one too, I don't think yet-another-email-app would have gotten nearly the same amount of press coverage that this has.)