I'm guessing most candidates don't have a lot of open source contributions, and "more open source" is one of the standard lines when they don't want to really explain why they passed on hiring.

Don't read too much into it. As an entry level applicant you're only getting a small fraction of anyone's attention and will need to apply Hanlon's razor to interpret most of your interactions.

In my experience the resume screen is a lot tougher if you want to work for them outside the US due to very low supply per demand.

It also depends on the level you're interviewing for. If you're shooting for a mid-level or even semi-senior role, that's very different than if you're shooting for a "has industry-wide impact" kind of role. In the latter case claims of prior impact will be carefully scrutinized to weed out poseurs and liars.

Yeah, it was only a new-grad, entry-level position, and they still wanted a huge volume of open source contributions. I don't know how most people would achieve it - mine were from internships and they still weren't enough.

Sounds insane. Based on our two experiences it seems like the requirements can change a lot. Hopefully if you apply again in a few years they won't require that anymore, but it's hard to say without knowing what are the factors that pushed them to require that in the first place.