PIP claim - immigration documents requested - already claims UC

Have a non-EU client with ILR, and already claims UC and HB.

He recently claimed PIP over the phone, and was sent a PIP.3009, stating: “To help us decide your current status whilst living in GB or NI please would you send your passport, travel documents and any letters you have from the HO…”
The letter goes on to say that if he doesn’t want to post originals, he can take the documents to JCP “where somebody will check your documents and pass the details on to us”.
I phoned DWP PIP, who confirmed that he has to submit the documents, despite already clearly meeting immigration reqs for other benefits. PIP can’t communicate with UC/JCP on a rudimentary level.

I just find it really confusing that he has to submit documents to JCP that they already have from his UC claim (claimed 2 months ago, with no immigration issues)!

We have seen a lot of this recently not just those with ILR. Those with no fixed abode have also been asked to provide additional ID docs before a PIP2 will be issued.