It also affords the coach to start talking to prospective teams right away, without the burden of getting a team prepared to play each week. It is like releasing a player early that you know you have no intention of keeping.
As for the Campo point, this is different. They are daring Jason Garrett to win and get the team in the playoffs for their own vanity. Say he gets there and loses, the result is the same. The only issue here is that they think they are showing loyalty and faith with him. If I were in his position, I doubt I would say thanks for the extra four week grind. Let me take a month off and refresh before looking for a new job.
That's the only difference from the Campo situation. They're still talking to candidates while Garrett is still on the job, effectively cutting his legs out from under him, as if that wasn't already made clear.
There's plenty of talk that they looked into replacements last year but couldn't find any that they liked markedly more than keeping Garrett. That's bad enough circumstances to return to. Then, the decide not to extend him and let him work as a lame duck coach all season. Followed by communicating with a guy like Meyer about taking the job before Garrett has even left the building. I'm no Garrett fan, clearly, but that's not great treatment of a head coach, no matter how you slice it.
And it's easy to see why the wheels are falling off this thing.