Right, but the software side of the stack needs a way for subsystems to say "I'm important, don't suspend", and that's what this systemd feature is for. The fact that it's based on top of an S3 suspend to RAM means that the laptop can't do it well, not that it isn't a useful feature.

(Also I have to quibble with the "very specific use case" idea: it's the standard use case. Laptops are the weird and rare edge cases these days.)

But on a laptop, I do want this case to be manual. Even on a phone, I would like to have more control over stuff like Notification and the likes (I think ios have background process or something).