This is an absurd change for many reasons. Not only Anet gave more utility to a traitline that already gives a lot of it and makes stealth more powerful, they forgot that thief has an entire traitline where half the traits to pick from are useless or way too weak.
It only makes sense, imo, that being superspeed a mobility effect, it would be better for build variety and balance in general that one of near useless Tier 1 major traits from Acrobatics be replaced by something that gives thief access to superspeed.
Anet repeteadly gives us proof that they have no idea about how thief works every time they make changes thinking stealth is the only thing thief has available.