What exactly do you find inexcusable here?
« 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.)
The fact that Intel does not do that with a bug of this magnitude shows how much respect they have for their users.