This has happened to me, but what it exposed was the hiring process gave absolutely no indication of whether the person could code. The 3 juniors assigned to me were interviewed by the VP, and I under him had no say or insight into the hiring process. 2 of them did super well and are now senior devs. One of them took up 30-40% of my time (with my putting up boundaries) and the basic understanding of the platform we were using never clicked for him.

The thing is - they got 2 very driven loyal devs out of it, and cheaper than normal at first. They also had an assessment period of 3 months after which the one who would take up all my time was let go. It was absolutely worth it for the company.