Why wouldn't Russia jump on this bomb theory. It would give them an excuse to “Unleash hell”. The fact that they aren't speaks volumes to me.
But what do I know.
I read all parties as saying the same thing just from different perspectives. The US and UK perspective is about deciding whether it is safe to have their airplanes fly in and out of that location. Russia is being careful because they must answer to the families of the dead. They have no motive to jump to any conclusion. They are already bombing ISIS so they need no additional excuse.
All parties are saying it is too early to say definitively.