DDR5-7600 is around the absolute top end of what is currently possible even on Z790/13th gen. That is with a flagship board model and a very good IMC (integrated memory controller) in your CPU. Because the IMC quality is just another silicon lottery, just like the quality of the normal cores. So this DDR5-7600 what experienced RAM overclockers using a CPU with a known good IMC can stabilize, if everything goes well. But i've also recently read a review of the EVGA Z790 CLASSIFIED where the maximum stable speed was DDR5-6800, using all the tricks in the book. So it depends on everything working well together, including the BIOS and its settings. Even just DDR5-7200 can be difficult to make stable, it takes the right BIOS settings to make it work, like you can see in
this video.
What you have to keep in mind is: XMP is never a guarantee, it's only a goal that can be reached in optimal conditions. So about the RAM speed that's on the packaging, you can buy RAM with whatever advertised speed that you want, but that only means that the RAM itself is capable of it. However, the following factors all affect if the RAM can run at a certain speed:
1) The mainboard model (PCB layer count, PCB trace optimization, RAM slot topology and slot count, component selection, RAM VRM etc.)
2) The mainboard's BIOS optimizations and the BIOS settings
3) Your CPU's integrated memory controller (IMC), quality depends on the individual CPU (silicon lottery)
4) The properties of the RAM modules.
So the RAM is just one piece of the puzzle in the memory system. If someone from the future brought back a kit of DDR5-8800, will it run at DDR5-8800 in any current hardware? Of course not. But the RAM itself is not the limitation. The board, BIOS and IMC are not capable of it at the moment, such speeds would require future platforms.
DDR5-7600 is simply at the edge right now, you definitely need to know what you're doing to get it stable. This is not some "plug & play" speed, this is something that enthusiasts buy to have the best potential on the RAM side (highly binned kit), and then do a back and forth of fine-tuning in the BIOS and stress-testing.
You can compare it to the early days of DDR4. For a long time the speed to get was DDR4-2666, then the platforms (boards/CPUs) became better, the RAM itself became better, and the sweet spot first became DDR4-3200, then later on it became DDR4-3600. Until this day, you can see that the most commonly sold kits are DDR4-3200 or -3600.
However, with you getting DDR5-7600 at this point of DDR5 development, it's similar to a time where everyone was only getting DDR4-2666, but you're suddenly getting one of the first high-end DDR4-3600 kits that became available. It's a similar sort of jump, from what is known to be fast enough and unproblematic at the time, to something completely enthusiast-grade that probably needs manual adjustments to work. At the moment, people are buying something like DDR5-5200/5600/6000. If they're a bit more adventurous, they may get DDR4-6200/6400 or so. But the DDR5-7xxx range is still reserved for those who really know how to handle high-speed DDR5 and don't shy away from tinkering with all the related settings in the BIOS.
Getting a high-spec kit of RAM to work 100% stable is like fine-tuning a race car by driving on a circuit. You need to drive a bit, come into the pits/garages for some feedback, adjust accordingly, and drive out again for more testing. No BIOS can automatically do that for you. The automatic settings only work for road cars, not for race cars. If you don't know how to make this work (and indeed it might also be impossible with your specific CPU's IMC), then this kit might've been a bit of a waste of money, because you would have to run it at DDR5-6xxx to stabilize the memory system.