You're probably right, in the short term, but I think the more games Black can get under his belt before next season, when he's potentially successor to Reynolds, the better.
But he's more likely to get a run in this first half before Mam returns, while having Hunt and Reynolds there means we're not so reliant on him to steer the ship.
We don't really want to debut him later in the season, when Reynolds inevitably goes down, and/or Hunt is on rep duty, without these two experienced chaperones to ease the pressure.
If we don't debut him soon, we're going to get Madden/Rogers/Walters as experienced stopgaps, and that's building nothing towards the future.
I'm not saying he did anything in the trials to demand selection, or even that he's ready. It's more we need to give him a taste for next year.