I had always imagined it as wire rims, where even if the lenses are unbroken you could get a bit of a gouge or a cut from the wire around the nosepiece.

Anyhow, it turns out that I may have heard an exaggerated version of it. This version merely has it as a bruise: https://www.google.com/books/edition/Traders_Tales/NyeVNsWvJ...

My sunglasses frame is hard plastic and would likely break with far less impact than the lens.