Based on experience, I tend to agree there. An inexpensive poncho is more water resistant than Goretex. You just have to try not to get sweaty because material that doesn't breathe will eventually backfire when you're sweaty (which is not preventable if you're skiing). The condensation and sweat will be uncomfortable, cold and maybe even frozen. You may not feel the discomfort while you're moving around, but if you were to stop and sit for awhile (like in survival mode), then you would feel the uncomfortable condensation and sweat.

USUALLY, while skiing or snowboarding, it's better to use a breathable material (like Goretex). A behavior of breathable material is leaking eventually after a certain amount of exposure to rain. As a general rule, I start to pack it in if it's raining too hard.