Chrome has a built-in option to set itself as the default browser and it 'supports' Xfce.
I.e., it adds "WebBrowser=google-chrome" to ~/.config/xfce4/helpers.rc but the "Preferred Applications" app doesn't recognise this.

exo has the google-chrome executable as an option to the Chromium helper file. This works fine to choose Chrome (even though named "Chromium") as the default browser from the "Preferred Applications" app but Chrome can't detect it (because it sets "WebBrowser=chromium").

So maybe we need an extra google-chrome.desktop helper file with "google-chrome" as the executable/icon and "Google Chrome" as the name.