Whenever I doubt a phrase, I often think it's helpful to see it alongside similar phrases. So
I got my hair cut at the weekend.
Who cut the hair? Probably the barber or someone, but that doesn't matter and the sentence isn't explicit about who did it.
His parents withhold his pocket money until he gets his household chores done
Who is eventually going to do those chores? Probably the boy, but there's nothing to say he won't manipulate a younger sibling into doing it.
After a long struggle with the rusty lock, we finally got that door opened
Who opened the door? I don't know. It might even have swung open by itself once we cut the lock off.
My computer has been running so slowly lately; I think I need to get it serviced.
Who's going to look at the computer? The sentence doesn't say.
You say you think
the verb 'get' does mean just to transform a situation to another. I don't agree with that: this construction seems to be about obviating the agency and making more a point of the accomplishment.