The article actually gets it wrong.

I am smart, the kids’ reasoning goes; I don’t need to put out effort. Expending effort becomes stigmatized—it’s public proof that you can’t cut it on your natural gifts.

No, I don't think that's it. At least for me, I have caught myself thinking many times "I'm not good at X, so odds are I won't be able to be one of the best at X, so it's not worth trying"

(My parents never praised smarts and neither did my teachers, but I unfortunately discovered far too early I could skate by in even the hardest classes with very little effort.)