This is just nonsense, and is simply a LAME attempt by these companies, much as ANY corporate company that sells products tends to do, to illegally limit their liability especially for anybody who wouldn't know better. It is NO different than car manufacturers who try to insist that if you don't use THEIR manufacturer specific lubricants such as oil, power steering fluid, brake fluid and engine coolant, and I don't mean equivalents, I mean THEIR exact products sold through their stealerships, it will void the warranty.
Or that if you take your vehicle anywhere other than THEIR service centers during the warranty period, it won't be covered.
Now, in some countries they MIGHT get away with that, but since most countries have even MORE stringent consumer rights laws than the US, and in the US the courts have already ruled that automobile manufacturers CANNOT refuse to cover the warranty on any vehicle simply because you did not use THEIR brand of lubricant, so long as you DID use the CORRECT specification of lubricant, and that ANY suitably certified service center or shop can perform warranty repairs (Although then, as a shop, you will have to submit payment requests to the manufacturer and wait which most shops will not want to do), they cannot refuse to honor the warranties on these vehicles.
This is no different. Intel and AMD would never have a leg to stand on if they even TRIED to not honor the warranty on something because you used XMP, AMP, A-XMP or EXPO, all of which are SPECIFICALLY CERTIFIED, by THEM, and further approved through THEM working with their board partners to establish exactly what XMP or other OC specifications are supported on any given board WITH a specific CPU installed.
Furthermore, since THEY are the ones that dictate the majority of the specifications that need to be adhered to when it comes to any given motherboard's default behaviors such as clock frequency, voltages and other CPU specific configuration settings, they could never justifiably argue in court that you had done anything they didn't approve of UNLESS you had manually made a change to the default configuration that did not specifically conform to specifications certified by them such as using one of the motherboard manufacturers overclocking profiles, or manually overclocking something using your own custom settings. Since XMP and EXPO are both certified BY those companies, and since their board partners specify specific support parameters for memory speeds that are determined by direct cooperation with the CPU manufacturer, they would legally never be able to successfully argue that you had used not recommended methods that resulted in whatever damage occurred.
Besides which, not once in 35 years has Intel, AMD or ANY motherboard manufacturer EVER even asked anything related to this subject when I've had to return a product that was still covered under warranty. Granted, for CPUs it rarely happens, but it has happened occasionally, and has specifically happened SINCE the advent of these overclocking memory profiles on both DDR3 and DDR4 platforms, and not once have they ever asked "Was XMP enabled when this happened" or "Were you using an aftermarket CPU cooler" like was also mentioned in the video.
It's pure BS and is only there so that they can reduce the probability of having to cover something under warranty if somebody who doesn't know better happens to go along with it.
We have consumer rights laws in the US at least that are highly extensive and the idea that something like wouldn't fall under at least one of those protections is ludicrous and laughable. But these big companies will ALWAYS try to push you around if they feel like they can get away with it, whether they are outside the law or not. It's no different than manufacturers trying to not honor warranties if you've removed the "warranty void if removed" sticker on many products. The courts have told these companies to STFU on that subject as well, so no, I do not believe either Intel or AMD would care to litigate something like this. It costs way TOO LITTLE for them to simply replace the part than could ever be justified by the legal expenses necessary to fight it off.
Never happen. Ever. So no, I think any company like Tom's Hardware that would stop recommending memory that is rated outside the speed of the standard baseline that is supported by the default JEDEC spec would be stupid and would likely immediately lose all credibility and probably not long after begin losing their entire following as well.