The power button is for switching the Belkin Thunderbolt 4 Dock on and off. I use my Belkin dock with a MacBook Pro. Everything works perfectly. I think it's a very good part :-)
The power button is only used to turn on the docking station, not the PC. Personally, I returned mine after several network problems. I received another one of the same model and the same thing happened, the network kept cutting out. Since then I've had a Dell docking station and it works perfectly!