Steve Just thought, maybe GTI Hubs with S3 Bearing Units, the TT uses S3 Front bearings on the rear of the TTRS, they mix and match Bearings and hubs to get an extra 10mm of track.
So the S3 bearings would be shorter to ensure the track on the S3 isn't increased when combined with alloy 3C0 hubs, so if somebody has put S3 hubs on GTI iron hubs that might do it.
Having said all that it could all be Bullsh!t
Hat.....Coat.......TAXI!!!!!!!!!