I actually think the Pakistani have a better claim on the koh-i-noor than India. Britain took it from the Sikh Empire which was centered in modern day Pakistan and disputed Kashmir (Both Gujranwala and Lahore are in Pakistan), and they in turn stole it from an Afghan Pashtun who inherited it from a guy who got it from the descendant of a Persian who stole it from the Mughal's peacock throne (Which WAS in modern day India).
There's a reason both the Taliban and the current Pakistani government have also requested the diamond, imho we just reflexively and culturally see Indian decolonial claims as more valid for some reason.

What is definitely true is that it doesn't belong in London.