Streaming and recording performance could be affected.
I think this will depend significantly on what 'streaming' means. The combination of layout tools, audio tools, endpoints, GPU hardware and GPU acceleration used, all would factor in.
For the 'pros', having only eight cores enabled while streaming is probably not going to be an issue. They'll have a workflow set up that leverages hardware processing before (audio equipment with DSPs for major processing steps, to limit VST use in OBS, for example), and after (using an external/secondary box for recording and streaming live). For these folks quality, ease of use (though not necessarily setup and troubleshooting), and reliability are paramount.
If there's a limitation to be found, I expect it to be found first by those trying to do all of this on the same box, 'in the box'. I'd balance that with the knowledge that a 7600X is plenty fast for 'gaming', so a 7950X3D with one CCD disabled or the future 7800X3D will both probably have enough grunt to spare, especially if GPU encoding is leveraged properly.
Power usage is impressive, but are we really impressed? It's turning off cores, and running at lower frequencies, and is capped at a lower temp of 89c, and has a lowered TDP, should a lower power profile really surprise or impress under those circumstances? If it could maintain the same clock as 7950X, and keep all cores running at the same time, and still have less power, I'd be more impressed by that.
Since AMD is able to keep performance up while reducing power usage - well, that's impressive. They did so while adding cache and increasing complexity.
Granted there's a pretty clear line drawn from decreased clockspeeds and voltages to lower power usage, and it looks like the 3D V-cache CCD is being binned for lower leakage, which should result in better efficiency at lower clockspeeds. So not inexplicable, but going in the right direction.
I wonder how much MS paid AMD to gimp their CPU by making it rely on XBox Game Bar. Inexcusable.
No need for conspiracy theories - AMD has been open about working with Microsoft to implement appropriate scheduling behavior for games on their dual-CCD parts that have one 3D V-cache-bearing die. From the benchmarks we've seen, while not perfect at launch (what is?), the solution is certainly working as intended, when it's working as intended.
Also note that AMD needs a software-based solution, since their scheduler isn't implemented in hardware (like Intel's P+E core solution), and that Intel still needed to work with OS developers to ensure that the P+E core arrangement was also supported.
For a personal example, while trying to run the FSPR Handbrake benchmark, I found that my 12700K running on Windows 10 last year would not properly schedule the Handbrake encode. This resulted in performance over an order of magnitude slower than expected, and I begrudgingly upgraded to Windows 11. I believe that this functionality has been backported to Windows 10 since, but as I've made 11 work for my needs, I haven't gone back and tested it.
As for 'why the Xbox Game Bar', well, I guess we should ask, how else should they have done it? How should it be exposed to gamers?