I was going to say the same thing, its all bull what they did. In any case, Hey will fail, most folks aint spending $99 per year for an email app. Hey will next appear in macrumors with the following news title and summary "Hey Mail app shuts down and asset purchased out of bankruptcy. Hey is the app that made a fuss in 2020 about avoiding Apple's 30% app store fee."
Actually, Hey is developed by the folks behind the very successful Basecamp app/platform, so Hey might go away at some point, but not in the way you describe.