I can see how this could be unfair, but working as a dev sometimes does require you to be on top of things in a high stress atmosphere. For example, what if you're proposing an excellent technical solution in a meeting but some jaded older engineer is hard to convince? If you can't outline your thinking in that scenario, your solution could be discarded just because someone was louder than you. As someone who used to have performance anxiety, I believe it's generally something you can and should practice for. On the other hand, if there really isn't a need for this type of skill, it totally makes sense to avoid creating interview environments where you are filtering candidates based on it.