As one who has done a fair amount of engineering in the past 30 years, I can
assure you that it is way better to have the higher tensile strength and
forgiving rubber holding this pressure than cork. Cut a thin slice out of
the next cork you take out of a bottle of wine and then pull on it and a big
rubber band of the same thickness. This was a secondary seal, not intended
to take any significant pressure, that is having oil pressure put directly
on it from inside the gasket itself.

According to CPA, there have been numerous failures. Nobody seems to have
died yet which is probably why no AD.

--
Roger Long