I can see why airlines probably treat this on a case by case basis. The way of the World these last few years would end up with the system being totally abused ....'Orlando death certificates' on Ebay ?
People will have friends throughout the World who have had family bereavements ...some wouldn't think twice of offering a death certificate so a friend could come and visit.
It's the genuine people like the OP who suffer.
Sorry for the loss of a loved one.