Generally, when it comes to an individual aircraft type's performance capabilities, controllers don't have a clue. Ocasionally the controller will throw something out to see if the pilot "bites." I'm not being facetious here. Controllers really do not know much about what an aircraft can or cannot do. With the termination of cockpit visits, the knowledge level continues to drop.
That being said, one would hope the controller has enough experience and judgment to always issue control instructions with which the pilot can safely comply ... but don't bet your life on it.
FAA 7110.65P
(Edited to add reference)