if they place hasn't primed the turbo proper then it could have already caused damage even though theres now oil in there,like running your engine without oil then sticking oil in,the damage is done,just trying to save you the hassle of sending the turbo back coz these guys know what oil starvation is like and will make your warranty void
if theyve just put the oil feed on and started it then it would take a bit of time for the oil to get round
phone the place that fitted it and ask them how the primed the turbo?