I know, with game development work I've been part of and seen personally the line is blurry to me so its sometimes easier to bundle it all together and slap a "it's not finished yet" label on it. How far into the development it is really decides the difference to me, but this is why I phrased it the way I did.
I'm certainly wrong to treat an ES card like this, but I am not as well-versed enough in the hardware development process or knowledgeable about it as I'd like to be yet so the differences are really not well known to me beyond some board changes or vbios changes, maybe drivers. With game console hardware development I am much more versed on the matter, but only up to a point, especially the PS3 related hardware, but general purpose hardware like GPUs I have a lot to learn.
For example the card a while back from Fouquin with the dual hdmi/dp port I would classify as more of a prototype, but its clearly labeled as an ES card because of that one feature alone, even though its otherwise identical to the others (that I'm aware of, beyond ports), but in terms of what the card is, that's far from what a prototype card would be.
BTW I kinda want that card for conversation purposes because it amuses me. I also wish it took off more, but in an approach more like that Xi3 steam machine's handling did, where it just let you plug both in physically and works as-is.