UKVI Refused to send Passport-ILR Application

Hi,

To explain briefly my situation,

I have applied ILR tier1 gen SET(O) on April last week.
Amendments for 2012/13, tax paid and amended with HMRC.
Received a letter on end of September saying that "They are unable to process my application in 6 months as they are awaiting info from other govt agencies".
still waiting for the decision.

As my Indian passport expired in November, so I have requested UKVI(filled and sent an online form) to return my passport to renew it, but today I have received a letter saying that "They are unable to send my passport while my application is still under process".

But when I have called the UKVI customer service they said I can request my passport and also I have heard from my friends that UKVI send back passport for identity purpose etc.. even the application is under process.

So why they haven't send my passport in my case?
Can anyone please let me know, if you are in this situation or have come across.

Thanks