It's totally plausible that Intel detected this bug independently with their own verification effort or through another customer. Matching different defect reports when "unexplained" or nondeterministic behavior is the expected result can be challenging.
I don't mind Intel keeping very quiet about fixed-in-microcode bugs that don't directly affect valid userspace programs, like
« Instruction Fetch May Cause Machine Check if Page Size and Memory Type Was Changed Without Invalidation »
or
« Execution of VAESIMC or VAESKEYGENASSIST With An Illegal Value for VEX.vvvv May Produce a #NM Exception »
but something like this should be announced clearly.
(I keep my microcode packages up to date, but I don't normally bother rebooting when an update comes in.)
It was reported to Intel who fixed it and did not reply to the reporter.
The contempt for users. I know what I do when a user files a real bug: respond to them, acknowledge it's a problem, tell them when it's fixed.
The fact that Intel does not do that with a bug of this magnitude shows how much respect they have for their users.
It's totally plausible that Intel detected this bug independently with their own verification effort or through another customer. Matching different defect reports when "unexplained" or nondeterministic behavior is the expected result can be challenging.
'Contempt' is far too dramatic of a word. I think what you mean is 'indifference'.