Is it normal for 2 of the same watch to have different coating amounts?

[OTX]

Hey guys,

Today I stopped by an AD and he had 2 GMTs on jubilee bracelets on display. They had different amounts of reflection on the crystal. One looked more clearer than the other. One had a reflection and one barely did. Is it normal to have 2 of the same exact watch with different coating amounts?. I know Rolex only coats the inner side of the crystal but I expected them to be the same. I looked at them in different angles and they were definitely different. Had anyone experienced this before?.