Your own quote proves my pointUS v. Nixon is the law and a UNANIMOUS SC said the right is not absolute.
swing and a miss...still have not cited any case law to refute US v. Nixon
In U.S. vs. Nixon, the justices said there is a “general privilege of confidentiality of presidential communications” that has “constitutional underpinnings.” It was the first time the court had squarely recognized executive privilege. It is “fundamental to the operation of government and inextricably rooted in the separation of powers under the Constitution,” the justices said.
The second paragraph of your quote is not applicable here. There is no crime contained in The Articles of Shampeachment and thus no hint of immunity. There is no pending or implied criminal trial