Last year I dropped an enormous cottonwood trunk with a similar "enclosed bark" split trunk. It also fell into separate pieces when it came down. Very large, very heavy! There was little doubt as to whether it should have been taken out.
I had a similar Ash tree that had three trunks like this one, all joined about 4' up, when it came down I was left with the three trunks approx 12' tall when I dropped that it split where the trunks joined each other through rot that was not detectable before hand, where it stood if that would have split through wind etc as we have had recently it would have caused all sorts of damage. Having the three trunks I think would have acted like more of a catch for rain water than this one.
Both of you fellows are lucky that the trunks didn't divide during the process of making the felling cuts. Especially if pulling forces were being applied.
I've had the same thing happen and I've been lucky like that too.