are we sure?
I was under the similar impression, but i did some more digging and unfortunately am out of hopium lol.
I dug through some US docs and found the adu891/cmbre is merely a replacement for the MBTS/CFMRE, at the time of the PAF order, the US was still exporting the latter, whereas the former was only just beginning to be deployed widely. It had only achieved IOC a few years prior. I suspect this is not an indication of a new missile order/induction, but rather replacing old/unserviceable kit.
View attachment 207806
Though, the Congressional Notification was pretty thin on detail and lacking, i would be surprised if the PAF was getting legacy CMBRE systems, over the plus, HOWEVER, perhaps the Plus is designed around P3I Amraams onwards, leaving the CMBRE for the C5's and older. I believe even the C6 received somewhat updated targeting systems, whereas the C5 was more a 'avionics bay back' upgrade, lengthening the motor and re working the flight control, without modifying the avionics stack, meaning the 120C5 retained the B's avionics, which may explain the potential older systems we're getting'?