A score of 90 is the minimum requirement for passing and that is the initial target score set for both Stage 1 and Stage 2 study paths. When a student reaches a score of 90 on their study path, they see a Congratulations screen with an option to "Continue studying".
If they select this option, their target score is raised from 90 to 100 and all of the study materials that were not required for the score of 90 become immediately available.
Because their target score has increased, they will no longer show up in the reports as "met target" but they will have some other designation based on the new target score of 100.
Depending on where you look, you may see "Target Met" as No instead of Yes, or you may see a graph bar that says they are "improving" instead of "met target". You can learn more about student completion reporting options here.
Students are encouraged to "continue studying" for personal growth and it has no negative impact on their certificate. Certificates are issued based on the student's hard score only -- not the designations you see in reports.
Students who choose to continue studying may see their score drop below 90 if they take a test and do not demonstrate mastery. They should not abandon their work on the study path if their score drops below 90. They should continue testing until they have a 90 once again.