I know that you already know this but you should ignore whatever you think the interviewers did to suggest you weren’t a good candidate.
Firstly, I think you’re overstating how long the staring was. I mean just time 20 seconds on your phone using the stopwatch... that’s a LONG time. imagine staring at another interviewer for that long in front of an applicant. Does it take that long to signal that you seem rehearsed? If anything maybe the interviewer fancied the other interviewer
I really just think they may have been looking at something that was on the other side of the interviewer or they felt awkward not speaking so they shifted their eyes elsewhere. If this isn’t the case then you could assume that maybe they did that to test how you react in stressful situations. I know that at almost every medicine interview they have some way of doing this. At mine there was a person who seemed proper pissed off every time I asked him to repeat a question (at the end we laughed but idk where that came from) because he was literally scoffing while speaking. Turns out he did that to my friend as well. Another one of my friends did an ANU grad interview last year and his interviewer called him a liar when he said he enjoyed watching a certain sport & supported a certain team but when asked if he watched any of the games recently he said no because he was really really busy with his honours stuff. The interviewer said it’s not a good look to lie in your interview. He ended up getting a spot in the course probably because he handled it well.
I’ve read on forums that some interviewers respond things like “did you really just use that example” when they ask a question like give me an example of when you’ve worked in a team. Turns out they did something like that for every applicant.
You get the point of what I’m saying. Bottom line is don’t worry