Gradle itself isn't written in Groovy; it's 5% Java, 95% Kotlin. The Groovy runtime is only spun up to compile and run Groovy buildscripts (i.e. the default kind of Gradle buildscript with a ".gradle" file extension.) If none of your buildscripts are written in Groovy, then you're not compiling or running any Groovy code, so that runtime check never executes.