I don't think he's asking for video cards to natively handle JPEG images. ISTM what he is advocating for is keeping the JPEG decompressed in memory in a YUV format rather than RGB. The savings come from the fact that the UV parts are downsampled, not from any sort of compression.
So since you already have to process the image, it doesn't seem like a big ask to convert from JPEG-flavored YUV to GPU-flavored YUV. But I'm not an expert, so maybe this is hard/lossy?
I'm fully aware that he's not talking about decoding JPEG images, and instead is talking about keeping Y'CbCr formats in memory and rendering with Y'CbCr.
It's not lossy. But Y'CbCr -> RGB is not as simple as you might think. My whole post was about Y'CbCr -> RGB conversion. It's doable; I'm not saying it's impossible. There's just several various flavors of Y'CbCr and correctly handling all of them (or at least the majority/most common) gets tedious.
Why does the GPU need to handle more than one flavor of Y'CbCr? Why can't the jpeg/PNG/whatever decoder be relied on to convert whatever flavor it uses to the Direct X/OpenGL flavors?
So since you already have to process the image, it doesn't seem like a big ask to convert from JPEG-flavored YUV to GPU-flavored YUV. But I'm not an expert, so maybe this is hard/lossy?