Yes, you can only have offline tracks on 3 devices. This has been in place since the inception of Spotify. It is part of their deal with record labels.
This isn't a question either, more of a statement.
There are a number of ideas, with the status set to case closed:
I'm going to close this now, as the discussion can continue in the idea threads, where the discussion technically ended with the case closed 🙂
EDIT: Added links & topic closed