I recently got a Filco, and it feels smaller too... I think the difference is the tolerances are much tighter than old keyboards, so the keycaps do not move with my sloppy typing style. The fact that the Filco is a more precise instrument take away the "slop" inherent in the older board I am used to typing on. You might be seeing something similar.
My hopes are I either get better at being precise, or I "break in" the Filco to have a slight degree of worn in slop.
I am sure by that time my keys will all be shiny, but I could really care less, unlike others on here who seem to feel that their shiny Filco keys are worse than a root canal.