I don't see the Tottenham argument. He has a far clearer path to playing time at Chelsea. Unless he's going to Tottenham to sit on the bench behind Eriksen/Alli/Son. I don't see him slotting next to Dier or Dembele in a deeper-lying position, either. All of those players are young with Son and Eriksen the oldest at 25.
At least at Chelsea he'd have an aging Fabregas, Pedro and even Willian, 30, 30 and 29 respectively, to learn from and starting stealing minutes as they start to wear down over the next couple seasons.
I don't see this as being anything but greed from Barkley. Of course his goal is not to fuck over the club he grew up loving, but he certainly doesn't seem to mind us being a casualty.
It doesn't really matter whether Koeman put him in that position with his criticisms or not; you would still hope for a little more respect from a boyhood blue.