I used to be on the hiring committee at Google, and sometimes we'd ask for extra interviews if the person was very strong, but feedback was mixed in a particular area. For example, if a candidate bombed one algorithms question but performed strongly on an algorithms question from a different interviewer, then we might want a third data point.
That happened for <10% of people -- it was really the exception case.
So I think b) and c) could be that process.
a) sounds like they were just disorganized -- which happens a lot with early stage startups. Takes founders time to learn how to hire well and I don't think any accelerators or VCs are providing interview training to their startups.