Error in exercise

I am very new to FME but it could be that there's an error in an exercise in the Advanced course, namely Performance-Ex5a-Complet.fmw. There's a Group By on NeighbourhoodName in the last Transformer: NeighborFinder. However, when running the workspace the NeighborhoodName attribute remains empty. It is only when I put a Reprojector transformer after both PostalAddres and Firehalls readers and set the CRS on LL84 (like the Neighborhoods reader) that the error is solved.