This is what Bloomberg's article refers to as "unrelated reasons" for Apple cutting ties with Supermicro in 2016.

> Three senior insiders at Apple say that in the summer of 2015, it, too, found malicious chips on Supermicro motherboards. Apple severed ties with Supermicro the following year, for what it described as unrelated reasons.

And then as an "unrelated and relatively minor security incident" later on.