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.