I have heard this before as well.
While I don't know if that's absolutely the case, it makes sense to me.

I'vé tried a few dozen 5x86s and I can't say that they're very strictly binned. More ADZs can do 160 at 3.45V than ADYs but definitely not all of them while there were some 160 capable ADYs too.

Rikintosh wrote on 2024-02-01, 20:28:

I currently have an ADW, and this ADZ appeared at a great price, but I don't want to buy more things to store them here. I read in some places people saying that ADZ supports higher temperatures because in fact the core was made to operate at 160mhz, but with the launch of the AMD K5, AMD feared that sales would be cannibalized, and therefore limited it to 133mhz, making the versions greater than 133 rare and intended for specific applications

I don't think so. I have ~10 Am5x86 some ADW and some of the newer ones > 2000. Except one, all of them can do 160MHz stable.