I recall this being present in IT contracts at least ten years ago, but some time around then people figured it out and started insisting on removing that section... though I actually personally saw something like this for the first time just last week. Fortunately, a client had just sent me the wrong form, but there's no way I would have signed it. It's just a matter of carefully reading contracts and making sure you know what you're getting yourself into.

No, although that is a common clause in employment contracts. The GP on the other hand is talking about the default ruling under California law. You're allowed side projects in the same field on your own time, so long as your contract doesn't say otherwise.

(As always, I am not a lawyer and this is not legal advice, etc.)

You're right in my case. That being said, I have no interest in competing - it's more for side projects.