Please create an empty file, switch on line wrap mode and fill the first line until you are one character short of wrapping.
Duplicate this line
Now create a vertical cursor at the end of these lines using alt+shift+down covering both lines.
Add some more text to the end of these lines simultaneously to force wrapping to start on both of them.
Observe that the new text is placed on the the first and third lines rather than the second and fourth lines as might reasonably be expected?