While what you say is true, the point about the JDK versions is mitigated a bit by the fact many things are backwards compatible. Although yes, if you jump from 8 to 17, you're going to run into some problems.
I'm not a huge fan of the gradle toolchain tool (I don't think gradle should be managing my JDKs and I would prefer if it could instead just fail the build if you use the wrong JDK version), but I do understand why it exists.
I'm not a huge fan of the gradle toolchain tool (I don't think gradle should be managing my JDKs and I would prefer if it could instead just fail the build if you use the wrong JDK version), but I do understand why it exists.