Yes, EMPTY is a fluid.
public final class FluidTypes {
// SORTFIELDS:ON
+ /**
+ * Represents the absence of fluid.
+ */
+ public static final Supplier<FluidType> EMPTY = Sponge.getRegistry().getCatalogRegistry().provideSupplier(FluidType.class, "EMPTY");
+
public static final Supplier<FluidType> WATER = Sponge.getRegistry().getCatalogRegistry().provideSupplier(FluidType.class, "WATER");
public static final Supplier<FluidType> LAVA = Sponge.getRegistry().getCatalogRegistry().provideSupplier(FluidType.class, "LAVA");
