The thing I do not get the most is the glee I hear. "I will never buy Intel again", "Intel was cheating all the time", etc.
Mistakes happen to anyone. There is no way of proving that there are no hidden issues in AMD CPUs (at the very least, IMHO, no practical way).
And, well, I do actually expect Intel CPUs to be validated more thoroughly (purely because Intel has more resources).
Something as complex as virtual memory and the interactions between the microarchitecture and OS can have any number of flaws, particularly at the margins of the system or legacy support. One side note is that I recall seeing comments about removing certain guard bands at the end of kernel/user space that would have kept a limited set of pages off-limits in case of chip prefetchers or microcoded instructions running over and crashing/looping.
AMD and Intel had varying amounts of memory off-limits in that zone, just in case.
The new paging scheme shifts the actual space into a new mapping, so some poorly handled boundary conditions are avoided.
If people are just flaking out about the KAISER issues because they've been coded, it might be an oddly escalated reaction due to people noticing. Whether validation can help may depend on whether Intel is trying to throw a problem that hasn't been specified in the public research into the same basket.
Side channel issues on their own wouldn't normally be caught by validation, because the results are fully valid. The design and system architecture didn't mandate invariant time, or absolute obfuscation of any incidental behaviors that could hint at the history or state of process execution.
More fundamental changes would have to happen to change what the accepted results are.
More fundamentally, some of these exploits pit the desire for the best performance against the need for secrecy. Sometimes being faster means something to those paying attention, and hiding that information may mean giving up some of that speed.
We may need to wait and see if it's all just about the KAISER proposal, or if AMD is playing loose with the situation in the other direction. Even if this is all a blowup about the original "KASLR is pretty sucky and has been for a while" fixes, there are exploits even in the source papers for that proposal that AMD was vulnerable from that the proposal didn't cover, and general issues where being cleaner about kernel and user space could help long-term.