The whole C-8/D-3 saga could just be a way of PAF and Pak Gov diversifying at an opportune time as opposed to getting anything better.
By 'opportune' I mean this has come around the time of trade and tariff negotiation, and the Trump admin has regularly pushed greater US weapon sales in these negotiations. For, Pakistan's part this could have meant when US brought up the issue, our very capable leadership would have said Huzoor, salute, we have always been ready to buy. So Pak Gov manages its exposure to US wrath in the Geo Political sphere,
@Oscar has already pointed out the number of visits Pakistani officials were undertaking to China, so this could be closely coordinated.
The PAF diversifies since now IAF have to plan for another attack vector. I do not think Amraam C-8 beats the Pl-15, it is silly to think a single pulse rocket motor could have better kinematics than a dual pulse. Even the info on Amraam-D being truely dual pulse is dubious. Some cite information from the known makers of Amraam motors. Some reconcile this ambiguity by stating the D varient uses a booster, this aligns with other informaiton about how carrying the D varient as opposed to the C8 variant requires modification to carrier platform software. The C8 is said to be replacement in place of earlier C variants.
Finally, people on here and else where have said that the only difference between C-8 and D is software, two things to recognise here. One, if D is a C-8 with a booster and additional changes to the software of launching platform (together with the expected difference in the missile software), then yes it could be sold as only a difference in software since you can conveniently ignore the booster as it does not form an integral part of the missile. Second, a difference in software alone could stand for a lot. The amraam D entered IOC in 2006, the latest announced tests were from 2024, based around 'flying the missile better', optimising flight trajectory and engagement logic could alone account for much of the 'added range'.