I expect that this info was comparing Panther with 10.2.7 (and maybe 10.2.x) which suffered from the errors in the battery life calculator.
These issues have now been fixed in 10.2.8.
Therefore upgrading to Panther would not provide any increase in battery life.
(I don't have Panther so this is speculation based upon what I have read on various discussion forums)
I hope I am wrong!