A rising tide lifts all boats. Increasing brand salience drives both penetration and loyalty. But penetration is what drives the growth.
Loyalty and penetration metrics are intrinsically linked. They reflect the buying propensities of people in the market – propensities that follow the NBD-Dirichlet distribution and Ehrenberg’s law of buying frequencies. Growth comes from nudging everyone’s propensity up just a little bit. Because the vast majority of buyers in the market are very light buyers of your brand this nudge in propensities is seen largely amongst this group – a lot go from buying you zero times in the period to buying you once, so your penetration metric moves upwards (as do all other metrics, including attitudes).