How to get `completionDateTime` values from the 'https://graph.microsoft.com/beta/reports/getAttackSimulationTrainingUserCoverage' API?

I'm currently working on a project that involves the use of Microsoft's Attack Simulation Training APIs. I'm trying to extract the completionDateTime values from the API to present in a custom dashboard for real-time data representation. The endpoint I've been using is 'https://graph.microsoft.com/beta/reports/getAttackSimulationTrainingUserCoverage'.

Despite my efforts, I haven't been able to extract the desired data. In fact, the completionDateTime values always show as null. I was wondering if there might be another way to retrieve these values that I might not be aware of. I've also tried using the Graph Explorer but still couldn't find a solution.

Any guidance or assistance you could provide would be greatly appreciated.