Slominers – “Why wouldn’t how he drives, under possibly stressful driving conditions, be objectively relevant for the girl to help decide if he’s a baal middos?”
Yes certainly bad middos can be seen under stressful conditions, and obviously the girl should take them into account. But even someone with very good middos could still easily get flustered, e.g. by having a close scrape with another car. This would then make him feel very stupid etc, and if he isn’t such a good driver he’d be even more nervous to start of with that this type of thing might happen. The girl on the other hand just sits there and watches the ride.
Besides, what chance does the boy get to see how she reacts under stress, if she is a baalas middos. I’m not saying its irrelevant, I’m just supporting Josephs point that it is unfairly balanced.