technically speaking, adding lash caps does change the geometry. it doesn't change the fulcrum point, but it does change the sweep of the rocker tip over the valve tip. also, moving the adjuster farther or closer to the fulcrum to change the ratio, also changes the geometry since the force applied from the pushrod needs to be greater since it is closer to the fulcrum on that side.
think of a teeter totter for a reference. it's all basic geometry. now replace the kid at either end with a valve tip and a rocker adjuster at either end. any time you change the position of any of the three pieces, your changing the "geometry", regardless of how much and regardless of the effect.