They must have unique names in order to map to the Part Definition (PDB).
In addition to what already was said:
In your example you would probably name them GND1, GND2 and GND3, but you could also name them GND_17, GND_19 and GND_26.
That also means that the software does not know that these pins should be connected to the same voltage and can not check that.
What I ended up doing was name them GND1, GND2, etc. then unchecking the net so it wasn’t viewable and in text putting in GND on all of them