] We are given all we need to understand the style being parodied – the tone, and language of narrator conveys it, and narrator’s voice is very clear here, isn’t it?

This clearness is the matter of vertical context. I can give an example of Oliver Goldsmith, staying more or less within the topic, as sentimental novel, along with Gothic novel, contributed to the compendium of books that were parodied by JA. Vicar of Wakefield was - with great probability - an early parody of the genre (of sentimental novel), but Goldsmith tinkered it so perfectly, that unsuspecting readers took it in all earnestness.

] No one who had ever seen Catherine Morland in her infancy would have supposed her born to be an heroine

Mostly, of course, because JA painted a wonderfully true picture of a young girl, and the esthetics of previous writers, as Clara Reeve explained in her work, right before the end of the 18th century, was to put the ideal in front of their readers - supposedly for imitation.

] There was not one family among their acquaintance who had reared and supported a boy accidentally found at their door

Is this a parte on Tom Jones? Perhaps...

] Neither robbers nor tempests befriended them, nor one lucky overturn to introduce them to the hero