Everyone fishing around for anyone saying anything about Intel chips ever, and then trying to shoehorn it into a current narative is the ignorance of the crowd. Every single chip has errata. In this case Theo is pointing at Intel's own list of defects in a revision/chip, which is profoundly unilluminating, and is completely and absolutely irrelevant.

The issue is not that the errors existed, but the risk some of them presented. Theo correctly identified an area where the risks were greater than generally recognized.

No, he didn't. Intel specifically states that the errata can allow unauthorized access to protected memory. Theo then says "oooh, that sounds scary!". Yes, of course it is, which is why it appears in the errata list.

You are misrepresenting Theo's message, which looks beyond individual errata, saying that collectively they amount to a significant change in how the MMU operates, and from that predicts a high likelihood of a then-yet undiscovered flaw that would lead to problems much greater than were then being acknowledged by Intel (and he said AMD was heading the same way.)

He was less prescient when he implied that it would take Intel a year or two to get beyond this.