I deliberately poured water onto my thinkpad T430 a total of 3 times in 6 years. All three times, I did it while the laptop was running.
The second time I did it, the laptop turned off as I was pouring the water. The drains are only so big; water can only move so fast through them. I had poured the water so fast that it overflowed the drains and the keyboard, and run into the motherboard.
I pulled the battery, keyboard, and access panels, and let the laptop dry overnight. I turned it on the following morning, and it worked without any problems.
So yeah, spill-resistant laptops have their limits. Dumping a quart / liter of water on them all at once is beyond their limits. And you may get unlucky with spilling onto the laptop in just such a way that it gets into something. In general, however, they seem to be very effective at preventing damage from liquid spills.
