We are modeling a cortical layer, so where this input comes from is largely irrelevant. The cortex is a homogenous structure that process inputs in the same way, no matter where the input comes from (for the most part). It only knows it gets connections to other neurons, but not what they are or where they come from.
In fact one region of cortex could get input from several other regions and sensory input at the same time. It won’t know this, it processes the input the same way.
There is a lot going on in our sensory organs that we are not modeling in HTM. The eye is very complicated, and so is the cochlea. The equivalent things in HTM are encoders (I’m sorry about the hair, it was a phase), but these are extremely primitive compared to living sensory organs.