To my not-a-lawyer understanding, it is fraudulent. Fine print is allowed to clarify an offer, but may not substantially alter the offer as originally made.

I could see an argument made that a reasonable person would know an offer to be limited to supported platforms, and that the fine print clarifies which platforms are supported. To me, though, I’d draw a line between unsupported due to underlying limitations (e.g. can’t serve 4k video on a NES) and unsupported due to seller-side limitations (e.g. won’t serve 4k without remote attestation). I’d see the former as a reasonable clarification of the offer, and the latter as an unreasonable alteration of the offer.

It's crappy behavior but I think screaming fraud is taking things a bit far. If you buy a Blu-ray from a website you don't come back screaming fraud because the browser or computer you you used doesn't play Blu-rays due to the DRM requirements. A refund request fits the scenario much better and the company's response tells you whether they are worth doing business with, not whether you were the victim of fraud. Some responsibility still lies with the buyer that they will understand what it takes to use the thing they are buying and not expect to rely 100% on the seller to verify everything for them beforehand.

At the same time... I think the behavior is pretty shitty, just not illegal, in that it takes minor up front effort to resolve. An explicit message along the lines of "You won't be able to watch in higher quality on this browser/device combination. Do you still want to purchase the high quality version for use on another device? You'll still be able to watch either version on this device, just always in low quality" goes a long way.