There's a mod setting to enable terrain variations. When the setting is enabled, you can cycle through the variations using the Rotate key (R).
In practice, this setting doesn't work well. If you rotate a blueprint you get a different texture, causing a ghost over existing landfill.
I assume that you have the setting enabled? If so, try disable it. The only times you should then get landfill ghosts over existing landfill if using different types. E.g. pasting grass over sand.
Pasting landfill over existing island in Sea Block will not consume landfill.