https://docs.gradle.org/current/userguide/compatibility.html
https://docs.gradle.org/current/userguide/compatibility.html
If you switch your Gradle buildscript files over to being written in Kotlin, the problem goes away, as Kotlin's runtime doesn't seem to use any similar explicit checks.
(Doing so also allows you to go further and test out EA JVM builds, e.g. Project Loom, which Groovy-based buildscripts have never been, and will never be, happy with.)
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.
This doesn't appear to be true just by looking at the Gradle GitHub repository. It claims that the code in the repo is 46% Groovy, 44% Java and 6% Kotlin