When I port my model from Blockbench to the Figura folder, the skin is turned into a 4 pixel arm skin.
Here is the model in BB:

Here is the model in MC:

The only thing that I could think of is somehow when porting the "skin model" to "generic model" in BB affects the model when ported to MC.

Have you hidden the vanilla model via script? It looks like there is z fighting.

Also, what you see in blockbench is what you get in figura. If as a generic model the model is 3 pixels wide, then it will be 3 pixels wide in-game.

Ah. I see what I did. For some reason, a while back while uploading my skin, I selected the "classic model." Nothing to do with the mod, which is good. Sorry for the inconvenience.