JAR file names provided by jtreg 7 now include their version.
This seems to break the detection logic for being run on a test machinery domain.
That detection logic, together with the "implies" implementation in the same class, seems to grant permission to run TestNG-based tests. Therefore, an explicit extension of the permission set is not necessary.
https://github.com/openjdk/jdk/blob/83dc2e3e45a946dd1302efb84baf3afaa9309ba4/test/jaxp/javax/xml/jaxp/libs/jaxp/library/JAXPPolicyManager.java#L164