Sure FOSS proves their ability to work in a team, but you also have to consider that, generally, FOSS contributions will be less impressive due to the limitatio

Sure FOSS proves their ability to work in a team, but you also have to consider that, generally, FOSS contributions will be less impressive due to the limitations of working in a group - in a long term project all the cool stuff is usually done and you need to get approval for big changes. That means your FOSS work is more likely to be stuff like bug fixes, UX changes, maybe a new export format. Then compare that to a pet project where there are no limitations apart from what you’re capable of, so I think naturally people will be driven towards that so that they can do whatever their vision is.