I suspect it'll only affect the top-tier cards. If you have a fully-modular PSU, I don't think you have to be concerned - just order whatever cable becomes necessary from Corsair or whoever. If you have a non-modular PSU, then yes, you may need to get a new PSU. But honestly, if you're prepared to spend 3080Ti money and skimped on your PSU, you don't get my sympathy.
I really don't think nVidia would do this (if it's true) on a whim just to annoy people, but I can see it from an engineering, marketing and legal standpoint. They have to weigh up the risks of stupid people (I include myself in that category

) just blindly plugging in the card, ignoring the warnings in the instructions, and using a single cable to bridge the two 8-pin connectors. It only takes a handful of reports of people's PCs smoking/melting cables or bursting into flame to cause a major PR shi..-storm and kill the product.