Perhaps you are doing something different. I have a K intel and a non-high end z790 motherboard and it's not cooking. Or unstable.
Granted, it's an i5 not 7 or 9.
As for user choice, that argument is completely flawed. Unless a customer is sold a CPU that will be overclocked beyond manufacturer defaults, unstable, and uncontrolable. Who would buy such a CPU? And if you are going to demand that everyone wanted to be prevented from having their CPU pushed beyond what is stable, go ahead. If motherboard manufacturers set limits higher than intel's default, it cannot be user choice. It also cannot be user choice when the user is not told how the motherboard is set when it comes to CPUs.
Really, it also cannot be user choice when non-K versions of some intels sell for a higher price than K models.
Checking PPP US right now (lowest available price):
12600K - $177
12600 - $273
13600K - $273
13600 - n/a :/
13700K - $344
13700 - $371
So tell me. Which one would you pick? Only the 13700 is reasonable of the ones i listed, because the K would need a $30-40 cooler. Even then they're the same price.
It doesn't have to be installed onto a z motherboard though. But choice of motherboard never involves likelyhood the CPU will be overpushed. Usually it's the opposite, and buyers worry whether the VRM will be good enough. On budget boards, it's sometimes feeble for i7s or i9s. Budget boards also don't have all the features a flagship chipset can offer.
So how can you argue that buying the best, the flagship, the most expensive and most capable is somehow also a known and accepted risk? Customers look at features, ports, durability, and above all price. And reviews. No review i've ever seen said don't buy this expensive motherboard, unless it was because a budget version offers similar features for a lower price.
There are extreme overclocking motherboards. And there are i9 KS models. Had you argued about people who buy and overclock those it would be user choice to push limits, but it's again the manufacturers who let the customers down. Or made an honest mistake and pushed too far.
The core of the issue is that motherboard makers know they can safely exceed intel's recommendations, and so they do. This would probably continue to fly under the radar were it not for recent instability issues. Issues that would not happed had they not gone too far.
They will probably back off with the next crop of motherboards.
Nothing here is the fault of the user.
But I guess it's easier to blame manufacturers for setting a 10% higher limit (or in some cases no limit) on an unlocked CPU than taking responsibility for your own ignorance and the consequences of your actions resulting from it.
Nonsense.