I saw that movie, and he was also hurt by far less.. PIS?
Strength is irrelevant here, but Li's treetop level leaps suggest he's in a one ton range himself, at least. More important Li has a HUGE speed edge, and enough of a skill edge where he can pace himself (He can basically casually block Wolverines claws with a twig, if he wanted to, and bounce away to a treetop or something if he needs a breather)
I know Wolverine fans love to believe he's immune to punishment, but that's never played out in the comics, and it certainly doesn't play out in the movies. If Li took out all of his organs in one swoop, it WILL hurt him. He's not the T-1000 from the Terminator movies, physical damage hurts him and slows him down, and heavy damage will take a least a little time to heal.