I think this is a dumb rule, because why wouldn't Diala hand the code thingy to Han Solo in the second mission of Twin Shadows? She's smart enough to open the door (insight), but has no idea what to do with the thing once she retrieves it (tech).

"A carried token cannot be retrieved by other figures, traded to other figures, or voluntarily dropped."

"Diala will strain to move twice and give the token to Fenn, Fenn will move give the token to Jyn, Jyn will move then activate the terminal." Two and a half activations to end the game after getting the token. The no swapping rule stops stuff like this and the issue of "which of these things takes an action?"

Because they don't want the game to be a 4x4 relay.

That makes sense.