No-one has mentioned the PCV - am I right in thinking that if you have one it will be somewhere along the breather between the rocker cover and the turbo?
If this fails you can pull oil out through the breather, into the turbo and then distribute it around the air intake system, which the EGR is attached to (indirectly but I guess an eddy will cause the oil to be deposited).
So it makes some sense for the EGR to fail as a result of the PCV failing, except that at so few miles I would think it would just need a clean rather than replacement - but if it's under warranty why not let them replace it?
For what it's worth I don't think either my diesel car* or my sprinter have a PCV valve, or if they do it is not working, both get a fair amount of oil in the air system and whilst I haven't had the sprinter long enough to say, the car just needs the EGR cleaning now and then. I have recently become aware that Wynns make a cleaner specifically for diesel EGR valves, which might be worth a try.
The common advice for PCV failure is either to replace it (it may be the plastic elbow on the rocker cover?) and/or fit an oil collection tank to the breather line - I quite fancy doing the latter but haven't yet worked out what parts I need or where to get them.
*now I think about it the car rocker cover has internal baffles which are supposed to trap the oil instead of using a PCV valve