I think rather than strictly looking at the definition of 'mechanical' to compare keyboard switches to, whatever shape, form and material used, actuation levels etc, it'd be certainly easier to assess what makes it mechanical by feel alone. There's a lot of cheaper keyboards with 'mechanical feeling' switches - seems as if it's the feel is what is aimed at being replicated, not the mechanism or anything alike. What is attempted to be copied is the 'clicky' or 'crisp' feel, whether in the feedback - such as tactile switches, or in bottoming out - like in linears, not a mushy dell robber dome.
I guess if you use a switch which can be considered to have the most mechanical feel, or possibly a switch that is most commonly associated with mechanical keyboards?, can be the used as a baseline of comparison and then determine whether or not it feels mechanical enough. But that raises more questions since its all subjective as to what 'feels' best.
