Two differing definitions. One is standard per the 3.5 rules. The other says:
Exception: Extra damage over and above a weapon’s normal damage is not multiplied when you score a critical hit.
I'm guessing they forgot the word "dice."
You may want to take a look at page 131.
Multiplying Damage: Sometimes you multiply damage by some factor, such as on a critical hit. Roll the damage (with all modifiers) multiple times and total the results.
Note: When you multiply damage more than once, each
multiplier works off the original, unmultiplied damage.
Exception: Extra damage dice over and above a weapon’s normal damage are never multiplied.
I do believe that the exception is referring to things like sneak attack damage and some magic items things like "flaming".
