Ann: Aqua Regia Testwork Confirms Nickel Sulphide Association, page-50

The point is that even though the implication is 99% of the Ni is in sulphides it may not be as simple as this and a significant portion of the Ni may be locked up in silicate minerals.

When these high MgO magmas begin to cool the first mineral that precipitates out is olivine at 1600 degC - Ni fits nicely into it's lattice - it gets first dibs on the Ni in the melt. Sulphides wont stabilise for another 1000 degrees or so. So there will initially be portion of the Ni in olivine - cannot be escaped. Over time the olivine is altered and can become serpentine (with H2O) or magnesite and talc (with CO2 present). As Blythefan said these minerals will be more amenable to digestion in aqua regia.

There are some cases where the cumulate can get hydrothermally altered and the Ni removed from the silicates into other phases, though this is relatively rare. Avebury in Tas is meant to be an example.

So i'm sceptical of the implied recovery - high resolution scanning techniques or a float test will tell us.