Shopify Software Engineer - Privacy interview questions

I was found in Linkedin by an engineer from the hiring team. We exchanged a couple of e-mails and after that I was asked to schedule a chat with a recruiter. Some days later I had a 20 min screening talk with a recruiter via Skype. She was very friendly and asked me many professional and personal questions. She explained the interview process to me and what will come next. One week later I had two more interviews in a row via Skype, of 1 hour each. The first one was what they call a "Life Story" interview, with the same recruiter. The next one was a technical interview with one member of the hiring team. My felling was great about these two interviews. I liked a lot of what I heard and I think the reciprocal was true. Another technical interview was schedule for a week later, with an engineer from another team. This time he went more deep in the kind of projects I worked on, asked for examples, which kind of technology I used, open source vs non open source software, nothing too dificult. At the end I also had a good feeling about this last interview. They were very kind and friendly all the time, but no one was clear about what would be the decision points to be hired. A couple of days later, the recruiter called me on Skype to tell me that they decided to not continue with me, because apparently my knowledge of open source was not good. This was very disappointing because after all, open source tools are easy to learn, but security and DPP knowhow, and mindset, are not easy to find, and I know I could contribute with that to the company.