This is because the learner has completed all the steps of their onboarding but has not generated and signed the compliance documents afterwards.
To have the learner's onboarding status change to 'Completed', please advise them to click on the Finish button at the end of their Onboarding Wizard steps. This will generate the compliance documents for them to sign. Once they sign the documents, the onboarding status will change to 'Completed'.