> They do not block unupdated phones because that will force users to buy exceptionally expensive devices to keep updated.

Hardly true, if they permitted Lineage and so on.

> Just like any enterprise software, it targets a set of common devices so they can provide support and QA on it.

Not really, there are a myriad of devices and they're not testing on all of them. A "pound sand if you're on an unsupported device and it isn't working" policy would be perfectly acceptable, as long as the issue isn't directly caused by the developer purposefully breaking the application for a subset of users that fail Play Protect check or whatever.