For Chapman and Eddowes, JtR was arranging objects from their persons, around them.
JtR was likely not stuffing his shirt or pockets with their organs. They went into something.
What likely happened is that somewhere between slicing their throats and the mutilation he is preparing some things to the side. Be it a bag that is open, or a sprawled out cloth, he uses something. He is sorting through things and preparing to take organs.
This would be an organized part of his profile while his targeting may be opportunistic, it suggests his attacks must have an element of planning.
The idea that Eddowes knew a spot in Mitre Sq. doesn't seem to sit well with me. There are two officers on the beat and well when it comes to Eddowes, she isn't exactly very good at avoiding officers. Then there is the problem of not being able to get into her doss house because it is closed.
I don't subscribe to the idea that JtR got lucky. He had some luck but he also appears to have planned a lot.
Mitre Sq., to have that level of confidence, suggests more than luck. He even laid out objects around her.
Bona fide canonical and then some.