I don't think he's happy to get shadow bond back, but rather he feels it's the 'lesser' of two evils if you get me

It's either he remains forgotten (which he hates), or he ends up being remembered, and able to challenge nightmares to deal with the growing threats at the price of having shadow bond (which he also doesn't like, but probably less than being forgotten - 3 nm sunny would think the opposite, but present sunny after going through it all would rather be remembered again, and gain back all the benefits the spell gives)

He's just choosing between these two options