The javadoc tag documentation spec for @systemProperty at https://docs.oracle.com/en/java/javase/19/docs/specs/javadoc/doc-comment-spec.html#systemproperty only includes a brief description of what it is. Compared to that, this mail https://mail.openjdk.org/pipermail/core-libs-dev/2018-November/056653.html which was sent when the tag was introduced, has much more detailed explanation about its usage. Specifically, the part which explains "Where should the tag be used?".
Adding some of these details to the tag specification documentation will help understand its usage better.