That hasn't been my experience (albeit with much smaller companies). For one thing, if you have correspondence showing that you've made a good faith effort to get an answer, it is going to tilt the playing field in your favor in a dispute.
But as going to court isn't what you want, this does lead in to something of a ProTip (though IANAP, TINPA): In general, when hashing out a contract, it can pay off to ask for various requirements imposed on you (in this case, it would be disclosure "within 30 days") to be mirrored by similar requirements on the employer.
I didn't plow ahead, I stopped once I thought it might have potential. I really only tried for the few months, after that they kept asking me permission to close the request and I kept telling them no. (I was pretty pissed).
No one will ever give you a yes or no answer. Never. It's like raising VC, or invading Russia. They will just put everything off until tomorrow. Forever.
I worked at That Place In The Valley that is not in Cupertino or Menlo Park. I tried to get "I own the IP" authorization for some side project that didn't matter to the business. I had a meeting every two weeks or so for a year and a half and nothing ever happened.
But now they know about it, and could make a claim if it blew up. So that's over.