Seems like just setting the organization up for some unnecessary criticism (if that's a thing for the Cowboys).If they cared about him, they’d let him go ASAP so that he can try for some of these other opportunities.
His contract expires in a few weeks. If they've told him that he wont be returning, then they don't need to "fire" him. He saves face - he wasn't fired, his contract expired - and he can still interview over the next few weeks for a new gig. Feels like they're doing good by Garret by going about it this way.