Learning Records Subject Area - Fields missing data

Summary:

A couple of questions - both relate to the Learning Records Subject area

Content (required):

1) Assignment Start Date vs Enrolled on Date (Active Details folder)

When I add Assignment Start Date to a report, it only returns data for around 50% of the records on the report, the rest are blank. Whereas if I use the Enrolled on Date field, it returns dates for all records on the report.

Is that expected and why is it happening?

2) Content Completed Date (Active Details folder)

Oracle documentation says this is "Completed date for the requested learning record" which I took to mean the date the course was completed by the learner. However it is not returning any results, so I'm guessing I've misunderstood.