I am using ArcGIS Desktop 10.4.
I have 2 feature classes in the same GDB. One feature class is a subset of the other one (i.e. it's a direct copy, with a subset of features retained, the others deleted). All 190 features in both FCs are identical.
My assumption then is that a union between these two FCs should yield the same total number of features as the source FCs (i.e. 190) because their geometries are directly coincident. However, it doesn't, and a number of slivers are created in the union shapefile.
Can someone please explain why this happens?