I actually had this weird glitch from the purchase date of my 6900XT (ASUS reference design), when GPU-Z would show a spike or two of a few thousand MHz on memory while testing. I think this is more of a software bug since if it did actually spike that high occasionally, it would hang/crash the system.
No idea how and why AMD allowed such sensor glitch and didn't fix it yet. Probably like with a few other software issues they have, they're just too gosh darn lazy to even lift a finger if it doesn't straight out crash to hell. Why is it that AMD has such great hardware specialists but аss-backwards software team?