The first person to complete the fifth challenge will not receive points right away, because the pact is not considered completed until their partner also does the fifth challenge.
When the partner also completes the fifth challenge, thus closing out the pact, they see their points awarded at that time. However, the first person will not see their points awarded until the next time they log onto the Daily Challenge web site (you will not experience the pact point award on mobile or on the Daily Challenge iPhone, iPad, or Android apps).