If you want to make it explicit, you can set up Hangouts to move your actual phone number to a separate "account" for only SMS, which leaves the only phone number from your gmail as your GV number.
It's worked pretty well for me, at least on Android. The Hangouts replacement for the web client is garbage, though.
It's worked pretty well for me, at least on Android. The Hangouts replacement for the web client is garbage, though.