Just an update, It was decided by the dealer to not replace the headliner or airbag. They apparently removed the rubber roof strips on both sides & the technician said he found a few other suspect areas that were all resealed.
Any mould found was cleaned up & sprayed with a material they use.
I was told I can bring the car back if the problem returns.
I think a key factor here was calling Nissan Canada & getting a case number, the Service manager asked for it.
I took this picture the day before I took the car in, appears to be some minor staining on the airbag. Certainly not soaked.