I am not too sure why everybody seems surprised by the T45/PAAMS issue - it is the nature of defence procurement everywhere on introduction to service:
Typhoon with no weapons (or anything else for that matter)
T23 with no computer system
Merlin with no ASW system
Lynx (Navy) with no missile
SeaKing (Navy) with no ASW sytem or weapons
T22 with no Sea Wolf
Spitfire with no guns
Sopwith Camel with no.....
I am sure the US etc have similar examples. In pretty well all cases the final product is world class in its prime role.