To quote Wikipedia, "There are as many ways of scratch-building models as there are modellers.." The essential probably lies in the personalisation of the making process. The end product may resemble something already produced either by another modeller, kit or even "RTR", but the mix of standard products, "spares" from kits or "raw materials" [such as acrylic sheet, wire, hemp, bits of plants..] could have something to justify the claim of scratchiness.
As a relative newcomer I enjoy using Linka plaster casting. I've ditched my "RTR" houses, church, station buildings and invested in carving tools and flat moulds. It's a long job, and as I'm learning on it I don't think I count any of those as finished, yet. With the best part of 3 metres of station platform just casting and modifying flat sections is a challenge.. but good fun. Am I a scratch builder? I like to think I'm an apprentice one. I also thank those who contribute to this thread for their inspiration and ideas.