I would venture to suggest, at the risk of getting vilified, that having fewer but larger pixels on the same size sensor can contribute to an appearance of greater DoF, depending on print size and viewing distance.
As Graham has suggested, downsizing the image which has more pixels to the same size as the image with fewer pixels, sort of equalizes DoF in both images.
But what happens if you upsize the image with fewer pixels, through interpolation, to the same size as the other image? In those circumstances, the image that started off with fewer pixels might appear to have greater DoF because the sharpness at the plane of focus will be less (than that in the image with initially more pixels) and will be closer to the sharpness of the rest of the image (in both images) which is not in the plane of focus.
Downsizing the image which has the greater number of pixels results in a discarding of resolution at the plane of focus, but no discarding, or less discarding of resolution away from the plane of focus.
Upsizing the image with fewer pixels is probably a fairer comparison because no information is thrown away in either image.
However, there might be a problem with the definition of DoF if it includes phrases such as 'acceptable sharpness'. To take an extreme example, a large print from a pin-hole camera might have amazing DoF, everything being equally sharp (or fuzzy) from one's feet to infinity. Pin-hole cameras are noted for their great DoF.
If nothing in the print is acceptably sharp, does that have a bearing on DoF? If you were to take a slightly fuzzy, image from a pinhole camera, digitise it and then through photoshop manipulation, seamlessly plant a sharp object ( figure, face, tree, whatever) in the middle of the image (or replace a relatively small object already in the image with a sharper version), would we have converted an image that we previously considered to have great (extensive) DoF into one which now has shallow DoF?