I've found our eVar/prop for raw referrers showing unfamiliar value "android-app://com.google.android.googlequicksearchbox".
However, default "Referrer" doesn't count such value at all.
The value of "Referrer Type" broke down by this raw referrer is "Typed/Bookmarked".
I discovered this is the value of referrer of Google Search App traffic.
Then is it appropriate to deal it as "No Referrer"? Should we treat it as search traffic?