Gear snobs.

[fdeck]

Not really. Many things are tradition. It's a little like not washing a uniform when you are in a hitting streak or not stepping on the baseline when walking on and off of the field. Part of being first chair comes with the expectation that you are responsible for helping a visiting soloist if something minor goes wrong. The soloist and first chair probably didn't think twice and had no hesitation when exchanging instruments. It was expected.

The concertmaster is even expected to pick up the baton if the conductor keels over.