I actually think it's a very fair characterization of how many people feel, based on their comments. Maybe not you, but I responded to your post earlier in this thread. I didn't intend to twist your argument, but I don't really think you're giving the staff any kind of credit. That's not hard to understand, the staff hasn't proven that they can coach up raw players and turn them into technically sound players. But it's not impossible.
And while I don't think he can play corner, I do see a benefit to exposing him to corner training. I think his biggest issue is tracking the ball and sticking to the receiver, so having to compete with receivers and corner will give him needed reps in pure coverage situations, even if he doesn't stay at corner. And if he shows he can do it, then we know we can use him as a matchup defender in big nickel and dime situations, like CBFL says.
I'm just saying, give him and the staff a chance, and let's assume they didn't just see a "TJ can play corner" omen in their oatmeal yesterday morning and decide to ask him to do something new. Why not assume they've actually thought it out and have a plan?