AMD Confirms Investigation Of Alarming Radeon RX 7900 XTX And XT Temp Spikes
That information comes from German site HardwareLuxx, who has been looking into the anomaly with the help of colleagues at ComputerBase and TechPowerUp. To be clear, it's normal for the hotspot temperature to be higher than the rest of the GPU; that's the point of that reading. However, it's abnormal for there to be such a large delta.

Compiling the results, it seems like this problem primarily affects the "Built by AMD" (BBA) reference models. While a PowerColor card seems to suffer the same issue, that card is using the AMD reference board. The largest gap that HardwareLuxx has observed is a whopping 53°C. When the hotspot temperature hits 110°, the GPU will start to reduce its clocks and throttle, even if it's fully-loaded and under its power limit.

Some users in the thread posited that it was an issue with the vapor chamber used on the cards, but if that were the case it would be more likely to manifest with the card oriented horizontally than vertically. The more likely circumstance, as HardwareLuxx posited, is that the cooler is making poor contact with the Radeon GPU. When oriented horizontally, such as when installed in a tower case, gravity can pull the vapor chamber away from the GPU. If the mounting hardware is poor, that tiny bit could be enough to drastically worsen cooling.

If you're having heat, performance, or stability problems with your Radeon RX 7900 series card, try laying your case on its side to see if things improve. If they do, or even if they don't, let us know in the comments below. Don't forget to grab AMD's new driver update for your card, too.
Update 12/29:
AMD reached out to us with a statement on the matter of the overheating reference design Radeon RX 7900 XTX graphics cards. Here's the full text of the statement:
“We are aware that a limited number of users are experiencing unexpected thermal throttling on AMD Radeon RX 7900 XTX graphics cards (reference models made by AMD). Users experiencing unexpected thermal throttling of an AMD Radeon RX 7900 XTX should contact AMD Support.”This response is in stark contrast to earlier reports that AMD was refusing RMA requests for overheating cards, but it seems like the company is eager to resolve the issue.