I've known producers and engineers to be credited many times when they probably haven't done much.
For example, I won't name any names, but I know that one producer produced the beat and did the "pre-mixing", sent it to the engineer who then finished it off with the executive producer of the album. All 3 shared the mixing credits.
However, that doesn't mean it's right. Like others have suggested, you've just given the engineer your ideas to help shape the sound you want. That's pretty standard. Most artists tell the engineer throughout the mixing process "the bass needs to be more prominent", etc.