en.wikipedia.org/wiki/Oprichnina#Organization

This appears to misstate the title of Ivan Lazhechnikov’s drama.

Authoritative sources identify Lazhechnikov’s play as Oprichnik (singular), not Oprichniki (plural):

• A recent Cambridge University Press article on Tchaikovsky states that the first censored stage work on Ivan IV was Ivan Lazhechnikov’s tragedy Oprichnik, and even cites the 1867 edition as Oprichnik: Tragediia v piati deistviiakh.
• The Mariinsky Theatre’s official page for Tchaikovsky’s opera says the opera’s libretto was written "after the eponymous tragedy by Ivan Lazhechnikov," which confirms that the source play had the same singular title as the opera: The Oprichnik.

So the article’s wording changes the play’s title from the singular to the plural.

This gets the release date of Part II wrong.

Turner Classic Movies notes that Ivan the Terrible, Part II was filmed soon after Part I but "was not released until 1958" because Stalin censored it. The British Film Institute likewise lists the film as "USSR 1946/1958", reflecting completion in 1946 and release in 1958.

So it is accurate to say the two parts were made/completed in the 1940s, but not that they were released in 1944 and 1946. Part II’s public release came in 1958.