I don't think you are correct here. From the FAQ [0] on the website linked by the post:

“Derivative works” exception – although a successful termination causes all of the rights to revert, this will not affect exploitation of derivative works created during the lifetime of the agreement, even after that agreement has been terminated. Once the agreement has been terminated, the grantee (see the glossary) may continue after termination to utilize “derivative works prepared under authority of the grant before its termination…[consistent with] the term of the grant” (to quote from the U.S. Copyright Act). This means that if, for example, an author granted a company a 50-year exclusive license to create a movie based on the author’s novel, that company can continue to use and exploit the movie even after the author successfully terminates the exclusive license. The company may not prepare a new movie based on the novel; it may only continue to use the existing movie that it created when the exclusive license was still current.

[0]: https://rightsback.org/faq/#So.2C_I_get_all_of_my_rights_bac...

Yeah, if you license something to use in your game then that item comes with a license term. You did not buy it and you do not own it. If you did buy it instead of license it, you would be free to do whatever you wanted with it forever. But you didnt buy it, you licensed its use.