Dr Polya, our Australian academic, has one good point. The writing of even honest history is a matter of selection and presentation of what has happened. Historical memory is selective. Cultures, like families, want to feel good about themselves, and they tend to repress the memory of the uglier details involved in acquiring their fortunes. The two Bengal famines Polya mentions are examples; they've always been well known to specialists in the field, but they aren't part of the popular historical memory because the English (and their American offspring) like to think of themselves as good, or at least well intentioned people, and their rise to wealth, power and influence as the result of virtue.
So why slap Jane Austen's name on this phenomonon and blame her personally? Two reasons, I think.
First, it's a successful publicity stunt. Interest in JA has taken her out of the exclusive custody of the literature professors and made her work part of the middlebrow popular culture, which is why so many of us are here in Pemberley having these conversations. Blaming JA draws attention to Polya's own ideas.
Second, it's an attack on what I think of as the Gone With The Wind view of history; the tendency to identify with and enthuse over the upper class lifestyle of a past age while ignoring the exploitation and misery that paid for it all. JA has become a hot property in current popular culture in part for GWTW reasons; the movies all show pretty people in pretty surroundings saying and doing delightful things in clever ways, and a superficial reading of the novels can give the same impression. (At least, unlike GWTW, the don't outright lie about the foundations of the system; they just keep it off stage.) Polya, I suspect, believes that the present well-being of the UK and its heirs (including the US) rests on ill gotten gains, and would prefer that popular attention to history be concentrated on what makes us ashamed of how we reached our present situation. The "Austenization" of history means the distractin of the popular gaze from those unpleasant facts that Polya believes essential for our moral uplift.