I would not take excuses like this for rejecting a candidate, especially a highly qualified/skilled candidate, at face value. Despite the pervasive rhetoric about wanting the "best" or hiring only the "best," both individual interviewers and companies as a whole are often afraid of hiring candidates who know more or are more skilled than themselves. The unstated fears include that the candidate will, if hired, outshine colleagues, his or her boss, or even, in some cases, the founder or CEO of the company -- especially in the case of startups where venture capitalists or other investors could be impressed by the new hire.

Since it is usually not acceptable to reject an applicant for this reason, some pretext will be generated. One way is to focus in on some area where the candidate is weak or different such as using a different software tool. Another way is to use trick questions or problems.

This is an article on how this was allegedly done in academia in the Soviet Union:

https://arxiv.org/pdf/1110.1556.pdf