No team takes preseason serious so it's not like you get the real competition you would in a regular game either. That includes players after starters sit and entire game plans. This is when ideas that coaches aren't sure will work get tested. So if Tennessee were to run a full on gameplan and everything to use towards the regular season, not only are they limiting potential plays/ideas from being tested, but they would still be running against other teams that don't care which really proves nothing. Preseason is really just a scrimmage practice.