Yes and no.

The critics weren't especially prestigious, at least not outside crime writing circles - this wasn't the Times Literary Supplement or the national broadsheets. They were relatively well known crime writers (rather than literary critics which is where you might smell a rat) but not people you'd know if you weren't in to crime fiction.

The level of reviewing she got is pretty much what you'd expect from a book published by a major publisher in hardback. Yes they put their weight behind it but they'd do that in all similar cases - by the time they've paid for a manuscript to be edited and published as a hardback they're going to do everything they can to get that book in front of people as they've made a significant investment.

You might even argue in this case that they'd be more likely to go easy - after all there is essentially no risk to them. If it fails all they have to do is leak that it's her and it'll shift a load so there really is no reason to go against what were presumably Rowling's wishes (particularly as she's known to be strong willed and not someone you'd want to piss off if you want to publish her again).

What sort of makes your point is that she was being published in hard back at all - a major achievement for a first time writer and if she weren't who she were handing that manuscript in she may not have been published at all, but if you make the comparison between this and any other crime hardback, there's no evidence they did anything special.

The same is true of the sales.

The article makes out that 1,500 copies was a failure. Had it been a JK Rowling book that would certainly be true, but for a couple of months sales of a hardback from an unknown crime writer. Typically a debut novel will sell a few thousand copies in hardback and given that it hadn't been out that long (a couple of months against a total hardback sales period of maybe a year) isn't unreasonable to think this might have hit a pretty solid level. To put it in context the first Harry Potter novel had a first print run of 500 in hardback.

TL;DR version: the research may be fine but there's little evidence tying what happened with Rowling to it's point.

It's a solid point. I wonder though if it being a british author (even before it was known as Rowling) and forwarded to british critics by the british arm of the publishing company may have had something to do with it. Less crime novels published in UK than larger markets perhaps?