I recommend this approach as the emergency nuke. As long as you commit to keep inbox zero afterwards.
I use the exact opposite approach.
My inbox is simply a message log. If I read something, I read something. If I don't, I don't. The number of unread will forever grow.
Things that need non-immediate follow up get snoozed.
Actually I do a hybrid of this--I archive all the messages I don't plan to read without bothering to mark as read. The only point in doing so is to gauge my incoming spam rate which I manage with unsubscribes, mark as spam, and rules.