I always thought this model was pretty worthless. I remember when they tried to apply it to the internet. It didn't quite fit, but they needed a model because intellectuals.
Nowadays "Internet" is mostly HTTP 2 for most people and then this model doesn't even remotely explain the structure of it.
I claim that by 1981, the OSI Model was already obsolete and that it didn't fit well, that was not a good teaching tool, that it has done more to beffudle than enlighten students. The problem being is that if you learned according to the modle, you are not aware of what you misundertood.