grammaticality - Position of the word ‘just’

I was just watching a tv show where they used the following sentence:

He probably just hasn't gotten around to it yet

It was a reply to the question, “Why didn't he inform you about it?”

I want to know whether it is okay to place the word just right after he.

The sentence would then be:

He just probably hasn't gotten around to it yet

– which sounds more natural to my ear. If this is not possible, could someone explain why not?