I would suppose you were looking at many more signs and metric, but then you say it only took you a few hours, so perhaps not ?
I’d assume that dev wasn’t actually writing alone, and people had to discuss the design, talk with the PO/stakeholder, review the code, eventually QA it, manage the deployments etc. Perhaps that poor soul was doing everything alone…but really ?
I can readily think of a few people in my current company that are absolutely drowned by merge request reviews and technical design work, even as their title is just “developper”. I wouldn’t be surprised if they haven’t written a line in weeks, and perhaps one or two fixes in months. They are absolutely critical and I would laugh so hard if someone buying us just fired them because they couldn’t bother looking at other stuff than code written.