The RX 6900 XT is AMD's most expensive Radeon product ever to feature a single GPU at $1,000. On paper it should be only slightly faster than the 6800 XT, while costing a bundle. That's all you need to know, but of course, we'll put it to the test, because that's kind of what we do here.
Three reasons, really. The yields for Navi 21 just aren't high enough for fully enabled dies to be used for 6800 XT models, as they'd barely ship enough out to make it worthwhile, and prosumer AMD graphics cards are likely to switch to CNDA too. There's only the one chip of the latter, but more will come. So AMD were stuck with a bunch of 80 CU Navi 21 dies - not enough to for 6800s, not much use in the professional market - that needed to go into something.
While I agree on the prosumer / yield point, I still feel that Navi 21 exists to show that AMD is back in the high end (maybe as preparation for their next gen) and to keep nVidia in check as far as what they can charge.
Oh, I agree with your point that AMD very much needed a best-of-the-best halo product to pitch against Nvidia, and for a lower price point. Had they an endless supply of 80 CU dies, though, that product would be the RX 6800 XT (in an 80 CU format). As it is, the dies had to go into something.
Are you referring to SAM or Infinity Cache? If it's the former, it will have no effect on ray tracing, as the BLAS/TLAS are stored in cache/local memory. If it's the latter, then programmers have no direct access to it.
Both products are ludicrously priced for the minor performance boost they have over their lesser siblings. The RX 6900 XT is 10% faster, on average at 4K, than the RX 6800 XT, yet it is 54% more expensive; the RTX 3090 is also 10% faster than the RTX 3080 but it's a ridiculous 114% more expensive. GDDR6X isn't that expensive!
That "reviewer" is Steve Walton, the best benchmarker in the business. One of the things that makes him the best is his clear lack of bias. He ripped into the RTX 3090 just as badly if not worse when he reviewed it. He believes, and quite rightly, that neither of these cards should exist.
Where did you see bias? RX 6900 XT may be better value then RTX 3090 but that's not saying much. It is still terrible value as you can see in the graphs you probably didn't even look at, if you did everything would be clear as day. You get almost exactly the same performance with RX 6800 XT for way less money.
The ending is a great example. Steve bangs on about how terrible the value is compared to the 6800xt and suggesting that those buying the 6900xt are fools with more money then brains, whinging about how this is destroying budget gaming.
