If you dont believe it I encourage you to try to start your own company while working somewhere else. You'll be mired in legal nonsense so deep you wont even be able to see clearly. When you become an employee you sign just about every right away you have to anything you do, ever, while working for the company. NDAs, Non-Competes, Invention Agreements, etc.

Sure, the company can't avoid paying you. But in exchange they get 2/3 of your waking life for 30-40 years and 100% of your production. Some companies are better, some are worse. All of them have lawyers that, should you cross them, will make you regret everything. I am at a relatively relaxed company (compared to FAANGs) and even here I had to go through a ton of channels and sign paperwork to even begin work on an open source project.