DWP asking for a years payslips for UC claim

We have had two clients this week asked to provide a year’s payslips (one from former partner!) on their journal to do list
Has anyone any idea why a claimant would be asked for this?  Can’t think of any scenario when this would be relevant

UC helpline couldn’t think of anything under than a grace period for benefit cap; not relevant in either of these cases

Anything to do with right to reside as an EEA national - maybe checking if has permanent residence status? (Or family member of someone with PR - could explain the partner request?)

I saw this too a few weeks ago with a client who has a terminal illness .
They want her to list everything that she earned from Jan 17-Dec 17 ( her UC claim was made Dec 17. ). She has been on ESA all that year. Also no EEA/right to reside rules apply here.

I advised her to ask in her journal why was this needed and that she was on ESA. I have no idea why this was generated and I haven’t been able to see if she has had a reply as she is undergoing further treatment and too unwell to check.

Any one know why this ridiculous question is being asked?