I would love it if OEMs started to do this.
Unfortunately, I bet that most OEMs will just license Chrome, and if they decide not to do that, my money's on them creating half-assed proprietary browsers built around WebView before they turn to Firefox.
Which is a shame, because Firefox for Android is young, but shows great promise.
All of the major OEMs have already done that. They've been shipping their own browsers built on top of webview for years now. The only devices that ever saw Google's/AOSP's Browser were Nexus devices and those running custom ROMs.
Being limited to WebView isn't a problem anyway - that's all the old Browser used. It's "just" a UI on top of WebView. Just like the majority of browsers in the play store are "just" different UIs on top of WebView.
i bet all that means is that they removed dependency on the stock browser from the base system. which is welcome for barebones images that want only one browser that is not the stock one.
Like I said, I prefer Firefox for its desktop-like features. But in my experience, Chrome has a faster response in the UI.