No offense, but your “view” on labor law sounds untrained at best and dangerous at worse. Please stick to what you know.
That being said, companies do this all the time, at least in my experience. I’ve worked at multiple companies that employee union and non-union employees. Unionized workers have a contract, which is one of the things you’re accepting when you unionize. Companies can offer new benefits, but I think most assessments aren’t going to see this as “literally illegal”. Some of the benefit differences I’ve seen firsthand is the amount of PTO, sick leave, and education benefits. I’m not a lawyer in the least, and Apple may be breaking the law in some other way, but this seems like a normal practice based solely on the number of companies that employ it.
As far as why this might be illegal, here's some background https://news.bloomberglaw.com/daily-labor-report/starbucks-n...