Isn't this situation a little different though? The OP wants to use a beta backup on the final build.While @Mlrollin91 is giving you solid, best practice advice as a counterpoint I've never made a fresh install going from beta to GM. I simply go from the last beta to the GM OTA and haven't had issues that way. I do however wipe out my beta backup and make a fresh one once I'm on the GM as those backups are potentially bloated. YMMV but it seems there's no harm in trying.
Isn't this situation a little different though? The OP wants to use a beta backup on the final build.
I completely agree with what you are saying and do the same exact thing (unless I have issues).