I can’t help but notice that if for you “nothing else could have happened than what happened”, then your definition of “could have happened” is so narrow as to become trivial.
Rather, I think that by “X could have happened in situation Y”, the laymen mean something like: even with the knowledge of hindsight, in a situation that looks identical to situation Y for the parameters that matter, I could not exclude X happening”.
I can’t help but notice that if for you “nothing else could have happened than what happened”, then your definition of “could have happened” is so narrow as to become trivial.
Rather, I think that by “X could have happened in situation Y”, the laymen mean something like: even with the knowledge of hindsight, in a situation that looks identical to situation Y for the parameters that matter, I could not exclude X happening”.