a couple things to consider. Hickman isnt the type, at least based upon his latest interview to explain everything that happens in a story:
Jonathan: Okay, so these are actually the same question. And although this is a spoiler and me clearly explaining the story (which I try not to do), I’m giving myself a pass in this case because the plan we started with at the beginning of the project changed during the publishing of it.
I interpret as being some things he wants to leave to the reader.
The second thing, Ororo pauses before going further into explaining the situation to Cecila in an effort almost not wanting to cause panic:
Attachment 88366
And to say that she was containing a bomb I dont think she would do especially in front of the kids as she would not want to make them feel any kind of way (remember all mutants are welcomed on krakoa) and seeing that she was ok with staying there with the twins why would she unnecessarily make a situation more grave than it needs to be? She wouldnt. She would dig deep, put on a smile, and fight until she couldn't anymore which is exactly what she did.