There's also the distinction to make between a philosophical lie and perjury. That is, it's not perjury unless it's directly relevant. Bill Clinton committed perjury when he said he did not have sexual relations with that woman because that was a tactic to cut off a line of inquiry directly related to the charge.

Where are you getting this from? This distinction isn't a feature of U.S. perjury law. If you knowingly say something false under oath, that's (at least theoretically) perjury, whether the falsehood is "relevant" or not.

Additionally, I'm not sure why Kavanaugh's lying about his high school drinking would be considered irrelevant to the allegation that he sexually assaulted someone while drunk in high school.