In other areas of the spatial analyst, the 4 nearest neighbours are used.... ie
http://desktop.arcgis.com/en/arcmap/latest/extensions/spatial-analyst/performing-analysis/cell-size-...
So, unless esri wanted to introduce some confusion into the mix, they would use the same approach or provide a caveat indicating otherwise.
And have you concern, or examples where this would be an issue in your work, or it for curiosity or clarity of method?
