I agree on your open source comments as far as, the only open sourced code a person has is personal pet projects. However, if you see someone has PRs and commits into something like the Linux repository or a major well known project, then their open source contributions could be very meaningful. As an example. If you are hiring for a position for a developer to work on garage band at Apple, if an applicant is an audio dev for FreeBSD, that is a pretty good sign the candidate knows what they are doing.