The onus isn't on Apple or Super Micro to prove anything (though it may make business sense to do so). The onus is on the ones making the astounding claim. So far they have produced no motherboard showing evidence of this type of tampering. All it would take is one motherboard that shows the issue. Until then, there's no reason to believe the story.

> I don't know why I should trust Super Micro investigating Super Micro.

You don't have to.

From the very first sentence of that article: "... an outside investigations firm had found no evidence of any malicious hardware in its current or older-model motherboards."

Company hired by company finds finding that will make company hire it again in the future. Not news. Not saying the story is true ofc.