UseImplicitStableValues was added before @Stable was moved from being package private in java.lang.invoke to public non-exported in jdk.internal.vm.annotation as a means to allow the VM to implicitly trust certain fields in the java class libraries as having @Stable properties. It was later made default true, and currently this only affects String.value.

However, since JDK-8150180 String.value is explicitly @Stable, so UseImplicitStableValues no longer has any real effect and can be obsoleted and then removed.