By that measure all of Scripture can be said to be part of the Magisterium, as they are all equally inspired of God, but (we are told) require an infallible magisterium to assuredly correctly understand them.
Which is simply an assertion which is argued under the premise that an assuredly infallible magisterium is necessary to establish writings as Scripture and preserve truth, dissent from which necessarily makes one a renegade. Which is not what Scripture teaches.
“dissent from which necessarily makes one a renegade. Which is not what Scripture teaches.”
Which is exactly what scripture does teach. But feel free. “The flesh availeth nothing”.