Chain of Memories This is SO puzzling.

Or...
These "data" are experiments of the Organiztion after they were defeated or something.

 

They don't bow, they just go from their fighting position back into their regular standing postion. And I agree with Azera - The Absent Silhouettes are fanservice. And I'm guessing Nomura didn't just want to make random fights that appear in the KH worlds for no reason, so since memories are a big deal in KH, it's probably the best idea the staff can use to make the reason the fights exist more realistic - Sora's old memories of the CoM Org. members returned to haunt him.

 

There data copies

 

Actually I think you've all got it wrong. They are the repressed memories of the members that died and have somehow manifested themselves to hinder sora's progress. Not ghosts and not data. When a nobody dies they cannot come back They fade into nothingness accepted by neither light nor darkness.

 

When they appear they don't appear from the normal ORG portals- they are surrounded by many numbers like you may find in programs or something- they are just data- like a program that is programmed to act and fight just like a normal member. Simple.

 

They are just data like what Ienzo said.They are also Absent (I can't spell that thing)s. That is why you can fight them.