Hypersmurf
Moderatarrrrh...
Even if they omitted the phrase the str modifiers do not stack, thus not allowing power lunge damage to be added to two-handed damage.
If they omitted the phrase, multipliers add.
Two-handed would be +0.5, and Power Lunge would be +1, for a total of x2.5 - like if you crit on a charge with a lance, the multipliers add.
But since it says "regardless", that's moot.
-Hyp.