I don’t think I can really fault any Android developer for wanting to use Firebase and be done with it, because it’s just so simple to implement, and generally easy to work with.
But some things should be more important than comfort, shouldn’t they.
If they transparently inform buyers about the account requirement and what that means, then they have done their duty and are compliant, I’d say.
Not that I like that.
But as long as the consumer knows everything they need to know to make an informed decision about the product they’re going to use, it’s all good.
Now, this decision also needs to be voluntary, so if there are some dark patterns or other carefully constructed circumstances bullying the consumer into accepting all the bs, then that would violate the GDPR.
But what is voluntary or not is hard to say, for many products and services. Can be argued either way, and you better believe it will be argued either way.