Comment by err4nt

The point of Chrome-only CSS (vendor-prefixed features) would be to allow Chrome or any other vendor to expose styling functionality to CSS authors in valid CSS syntax in ways that won't impede future standardization efforts (like writing non-standard CSS would do) or interfere with that same CSS being processed by other vendors.

But this article isn't an example of Chrome-only CSS, this is about a change to the standard select element to make it customizeable in a standard way. It's not fully frozen yet, so they're seeking feedback and still working on it, so if you have input to give about this feature I think they'd welcome it. This blog post was about Chrome introducing experimental support for it, likely so developers can experiment with it and provide more valuable feedback towards its standardization!