I don't think that's what people were surprised about. Just speaking for myself, I was originally surprised by the statement "lying about your employment history to salt is also protected activity". After all, it's seems to make perfect sense that I can be fired for lying on my resume.

The bit that I didn't understand, and that some of the comments here cleared up, is that only lying about the employment pieces that specifically relate to past work as a union organizer are the things that are protected activity.