Awesome. They can do that, and I will work for the multitude of companies and startups out there that will not unionize.
You can't unionize every startup in the world, and non unionized employees will be able to demand a premium.
Other people are free to burden themselves with union rules, and I will be free to accept the higher salary that I can command because my competition is hindered.
It is a competitive advantage to not be burdened by union rules.