You've got the topic of the conversation somewhat wrong. The problem discussed above was that some people are simply bad at handling the kind of stressful situ

You've got the topic of the conversation somewhat wrong. The problem discussed above was that some people are simply bad at handling the kind of stressful situations that interviews present them with. (Note, it's not necessarily about any stressful situation, just one where you're under intense scrutiny.) Hence, you can end up not hiring someone because they're struggling to show their skills in an interview, even though they'd be an excellent hire otherwise (including being a great team member). This is, indeed, unfortunate.