I think the operative phrase there is 'related to the employer's business' -- the other issue is noncompete / IP assignment clauses will be written to be broad,

I think the operative phrase there is 'related to the employer's business' -- the other issue is noncompete / IP assignment clauses will be written to be broad, then they force you to win on merits: you have to prove it doesn't relate to their business, and if you lose (because courts introduce a degree of randomness), it doesn't matter what the protection was. And of course, that possibility has a chilling effect, which is sort of the point of the overly-broad IP assignment. (But yes, you're totally right, I was conflating IP assignment and noncompete... I've been tangled up in both.)