Unfortunately like others have said on your other posts on other threads, why the visa office has requested this is only known to them...
Got passport request May 22
You should also note that visa offices can request any documents they believe are necessary to process an application.....
My mum was asked to produce a Police Clearance Certificate... and we just provided it and she got her visa valid till the expiry of her passport...
So in a nutshell... juss comply with any request that comes from the visa office...it is for your benefit after all...