No, IKEA dressers are categorically not pre-fabricated. Basis for my assertion: IKEA and other flat packed furniture arrives in a “some assembly required” state, compared to “normal” furniture which arrives from the factory fully assembled and ready to use. Nuts like me that have their own personal wood shop and build their own furniture from scratch are the exception, rather than the norm.

In the aviation world, there’s a category for Experimental - Amateur Built aircraft. There is a rule for certifying an aircraft in this category: The amateur builder must perform 51% of the fabrication and assembly of the aircraft. There’s this whole points system for figuring that up as well. There are kit manufacturers, but they can’t offer “We cut all the material to their final size, drilled all the holes etc. so all you have to do is rivet and bolt it together” because there’s no way to make that total up to 51%. They can give you enough sheet stock cut to rough size for you to fabricate wing and fuselage panels out of, provide an engine, etc. These airplanes are often informally referred to as “kit-built.”

I think “kit-built” lives somewhere between “from scratch” and “pre-fabricated.”