Your logic doesn't work this year.
Florida beat Tennesse 59-20
Georgia beat Florida 42-30
So, by that failed logic you use, Georgia should have beaten Tennesse by 51 points. However, Tennessee won 35-14 over the currently ranked #10 Bulldogs.
For fun, let's try another one...
Alabama beat Tennessee 42-17
Georgia beat Alabama 26-23
Again, using your failed logic, Georgia should have won by 27 points over Tennessee.
Matchups, injuries, location, etc all factor into each game individually. The Vols lead the all-time series against LSU 20-6-3. As talented as LSU was last season, it took an injured QB and blown referee call at the end of the game for LSU to pull out only their 6th win in the series against Tennessee.