This deal seemed a little fishy from the beginning, since it was originally reported backwards, and still would be a curious fit. The Timberwolves already have three first round picks -- numbers 4, 16, and 23 -- which means they don't exactly need a fourth.
Additionally, trading multiple picks to move up more than a selection or two is fairly uncommon in the NBA. On occasion a team might include a second-rounder to bounce up a pick or two, but according to normal draft values the 28th pick hardly seems valuable enough to bump the Grizzlies all way into the mid-first round.
One scenario where this might fit, however, is if the T-Wolves were planning on using the Grizzlies selections in other deals. Selling both picks could net them around $6 million in cash, while selling just the 23rd would only make the Wolves $3 million. If the Wolves feel the financial need just to sell one pick, it might be worth it to keep three first rounders with the cash since their roster has so many holes.
My guess, then, is that the Grizzlies have approved the trade, especially since this team really doesn't have the minutes or roster space for three first rounders, and are waiting on the Wolves to see whether they need the extra first-rounder because of an unrelated deal. Either way, don't expect to see action on this before draft night.