Can confirm I've fought manufacturers on their 'dead pixel policies' before in Oz and won, with the help of the ACCC. Basically a defect is 'Anything that would prevent the consumer from buying one instance of a product over another instance of the same product if they knew about it in advance', and dead pixels are considered defects by this definition, and manufacturers can't refuse replacement on defective products, period. The '7 day' or '30 day' policies are also not enforceable, if you get dead pixels 9 months down the road they still have to fix or replace. Even if it's 1 dead pixel.
Nintendo will not be able to enforce this policy here, though it might be quite time consuming and tedious to make them comply.
(nb: I am not a lawyer but I've been in this boat before)