The official dock has each of its ports fully fleshed out. These cheapie docks do things like connect the ethernet port to USB 2.0, use a "4K, but only at 30hz" HDMI spec, etc. You also get firmware updates from Valve.
As much as i want their efforts to get supported, the dock might be worth the price, but you don't really get much for the price of the dock in comparison with a mid-tier for example Ugreen dock.
UGREEN USB C Hub 7 in 1 USB C adapter with 4K 60Hz HDMI, Gigabit Ethernet RJ45, 100W PD, SDµSD, 2 USB A 5Gbps
40€ now.
4k 60p might be good for media playback if that's a usecase, otherwise you will find yourself in 720p or 1080p in some exceptions.