When I tried this, it had no effect. The build was compiled for JavaSE-11 even if jdk.version=1.8.
What do you mean by "the build was compiled for JavaSE-11 ? Aren't the class files not using the Java 1.8 class version?
If not, it's an important bug so please report it. However, a better and more portable approach (with PDE) is to override the source/target levels in build.properties.
I guess other issues are consequence of the workarounds you've found, so let's focus our attention on this root cause at the moment.