As for the time limit, it's relative. All things equal, if you can complete the problem in 10 minutes and the company can hire somebody that can complete it in 9, then objectively the other candidate is the stronger one.
As for nervousness for being forced to partaking in a stand-up performance, I'd argue that "social performance skills" can work against you, since the more "antisocial" you are, the more you can ignore (or are oblivious to) what other people think about you and you can focus on your task. It's only people who actually have the minimum requisite "social skills" that would be conscious of other people intensely watching them "perform".
But even if you're right -- interviewing is inherently a "social performance" activity. If you're not coding you're doing some other stand up performance to present yourself anyway.
As for nervousness for being forced to partaking in a stand-up performance, I'd argue that "social performance skills" can work against you, since the more "antisocial" you are, the more you can ignore (or are oblivious to) what other people think about you and you can focus on your task. It's only people who actually have the minimum requisite "social skills" that would be conscious of other people intensely watching them "perform".
But even if you're right -- interviewing is inherently a "social performance" activity. If you're not coding you're doing some other stand up performance to present yourself anyway.