The change for JDK-8221644 did not include the dynamically created script tags in file src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclets/toolkit/resources/script.js.

We have fallback code which will fetch the unzipped index files if loading of zipped files failes, which is why I did not notice this in manual tests. Still not sure how I didn't catch this when grepping through the source code.