They signed him 6 years ago when he was 16 so I would argue he has come through their acadamy the same with any of the players we have signed from elsewhere in that age bracket has come through ours, like Bogarde.
I'd argue that you need to spend a period of time playing for academy teams to "come through an academy". He was a first-team player at Fulham, went straight into the Liverpool first team squad, spent a year playing in the Championship for Blackburn and then straight back into the Liverpool first team squad. I think he might have played a dozen or so games in their U23s.
I'd say it's bit more like saying that Duran came through our academy than the Bogarde comparison - he was signed very young, but he was signed very young to be in the first-team squad rather than the academy.