The achievements are rewards in itself. It shows your gamerscore on your profile. So it displays your accolades, they won’t go unnoticed. For 152 on the other hand, there’s no achievement for that. The reason why they’re even rewarding players who reach 152 is because there initially wasn’t much of a reward other than the emblem that comes along with it. Not only that, it’s way too easy to mod/hack achievements Xbox.
Imagine a damaged Mark 6 or even HelioSkrill in Infinites style as a reward