As Tim said, it is the first match, so if both services have the same matching conditions, only the first will match. The second will never be evaluated.
Maybe you can explain what you try to achieve. If that is that OnGuard/posture is optional, you just enable posture in the service and in your enforcement policy you can check if there is posture information and depending on both the availability (status: UNKNOWN) or a known status (HEALTHY, INFECTED, QUARANTINE, etc), you can decide what access attributes to return. Merge the two services into a single one.