The Son of Man who is still in heaven

While I'm in the mood to discuss textual critical stuff, one variation which fascinates me is John 3.13

"No one has ever gone into heaven except
the one who came from heaven—the Son of Man"

Yet several witnesses (A, Caesarean text, 050, 063, f1, f13 et. al.) adds a little bit on the end.

"No one has ever gone into heaven except
the one who came from heaven—the Son of Man who is in heaven"

I don't have my library with me so I have no John commentaries and or Metzger to consult to find a solution (but the good news is that my stuff arrives on Monday, only took 4 months for the stuff to get here from Brisbane :| ).

Does the addition "who is heaven" convey the idea that Jesus' divinity (the Logos?) was still in heaven whilst he was on earth?

Hmmm. Has anyone written a Ph.D on this variant?