Not seeing the contradiction. The two sentences suggest a distinction between novice task completion and supervisory (ie, mastery) work. "The role of workers often shifts from performing the task to supervising the task" is the second sentence in the report.

The research question is: "Although the use of AI tools may improve productivity for these engineers, would they also inhibit skill formation? More specifically, does an AI-assisted task completion workflow prevent engineers from gaining in-depth knowledge about the tools used to complete these tasks?" This hopefully makes the distinction more clear.

So you can say "this product helps novice workers complete tasks more efficiently, regardless of domain" while also saying "unfortunately, they remain stupid." The introductiory lit review/context setting cites prior studies to establish "ok coders complete tasks efficiently with this product." But then they say, "our study finds that they can't answer questions." They have to say "earlier studies find that there were productivity gains" in order to say "do these gains extend to other skills? Maybe not!"