opera is never going to allow us to disable tab snoozing. the whole point of snoozing background tabs is to force us to watch ads on youtube (the most commonly used site in the background). the "save memory" excuse is just a farce to cover up the real motivation.
i honestly expect the "disable tab snoozing" setting will simply disappear in a future update. it's probably only still there so that google can test to make sure that ad-revenue sites never snooze.