Note the curvature, and how it's concentrated in one area of each stud's length.
Are the studs behind the duct, or under it?
I can't eliminate the possibility that the studs are precracked, jammed in place to hold the ductwork while it's being secured by other means.
I.e., one ductwork installer working alone, scrounges a few studs from another trade's stock, drives his truck over them to make them a little easier to compress axially by hand, and uses them as temporary support.
Mike Halloran
Pembroke Pines, FL, USA