Well, the NFL only has itself to blame for that. If you make a rule that you have to interview black candidates before announcing a coach, you're going to end up with some situations where it's pre-determined and you're merely "wasting" the time of the black candidates. I would guess it's still a net-positive, even if those few coaches are sometimes getting the run-around. Maybe not fair, but those candidates that have their time "wasted" are laying the ground work for others that come after them. Additionally, if said black candidate thinks it's already determined and they have no shot, then just decline the interview. It's not like they're being forced to interview.
At the end of the day, a lot of from the team's perspective is "You're damned if you do, and you're damned if you don't". If they do hire a black coach, inevitably when he's fired (which happens to almost all coaching tenures), then you'll get called racist for not giving him more time/support. Happens like clockwork, as I can remember that happening every time a black coach was fired in this market.