Because that page uses outdated info, and going by the new canon, Turbolaser bolts are made of Tibanna plasma, which HAS mass. So, there's some regular kinetic energy being delivered there.
That the Falcon can withstand megaton hits, given that the TIEs that are attacking it - TIE/fo Fighters, which are shielded and more powerful than TIE/ln Fighters - aren't even dishing out kilotons worth of damage, and are still considered a threat to the Falcon.