I'm modifying the default village structures in Recurrent Complex by adding in a few modded blocks to replace certain decorations (i.e. no pistons for tables), and I came across a certain problem with how the blocks would variate between villages.

While most of the wooden blocks would variate between biomes properly, this could not be said for objects such as the wooden slabs, meaning that even if most of the house is made out of Acacia wood, all the slabs will be Oak no matter what.

So as a quick test for the slabs, I used the "Replace Property" transformer to change the "variant" property to spruce for all of the Oak slabs.

This did absolutely nothing.
So for my next attempt, I instead tried to use a "Replace" transformer for the job.

But even after that, no difference was made to the structure at all. I browsed the wiki, and it says that I should be doing this correctly, so what gives?