I think the FDA is saying no post hoc combination of data from all 3 trials. They want to know the statistical analysis plan ahead of time, combining severe and critical from CD12, CD16, CD17, and whatever will be the US critical trial that just got approved. It is good news that they will allow/consider combination from all 3 or 4 trials. That should definitely help with statistical power.
It may be hard to combine with different dosing, however, data from CD12 (2x subcutaneous dosing) with CD16, CD17 (4x IV dosing), and US critical trial (4x IV dosing).