The stratigraphy of a finish is rarely that tidy, for two reasons. The first is that all of the layers are extremely thin, and some are so thin as to approach the vanishing point. The second reason has to do with how soluble and permeable those thin layers are. Solubility and Permeability Solubility describes what will dissolve in what. For example, shellac is soluble in alcohol, meaning that if you add solid shellac flakes to the solvent alcohol, the shellac dissolves and you get a purely liquid solution of shellac and alcohol.
Permeability is a measure of how porous something is.
Wax may not be soluble in alcohol, but it is permeable to alcohol. Much as water can soak through a cotton shirt, alcohol can diffuse through wax. Solubility can come into play when a new coating is applied. Solvent strippers take the effects of solubility to their logical, disastrous extreme. If old layers aren't soluble, they may be permeable.