It seems that by default that RasterToPolygonCoercer transformer joins polygons if they have the same value as the neighbouring cell, as seen below:

 

 

And there seems to be no option in the RasterToPolygonCoercer to stop it from doing this.

 

 

What is the simplest way I can fix or avoid this aggregation of cells to larger polygons - either by using a different transformer(s) to coerce the raster, or by further processing the polygon output?