We don't review every novel of this type. Very few of the Plaidys, either the Three Rivers trade pbs or the UK editions with the attractive new covers, have been revisited by us. It all depends on space, whether publicists decide to send them, and whether the editors think they're worth extra attention. (At the risk of derailing this post, I'll mention that some Victoria Holts will also be reissued soon, but the covers are, imho, garish in an odd psychedelic way and a little creepy.)
It struck me while reading the 1/29 Publishers Weekly over lunch that HNR isn't unusual in sometimes reviewing new editions of older books, although I haven't seen this done in PW very often. On p.42 I found a very nice review for Orson Scott Card's Saints, in its new Subterranean Press edition. Saints is a historical novel about Dinah Kirkham, a heroine of the early Mormon church; born in Britain, Dinah lives through the Industrial Revolution of the early 19th century, converts to Mormonism, and emigrates to America, where she becomes one of the wives of Church founder Joseph Smith. The novel has an interesting history in itself. First published in 1984 by Berkley as A Woman of Destiny and marketed as a romantic saga, it was renamed Saints and republished by Forge as a mainstream historical in 1988. It also appeared as a Forge trade paperback in 2001. (I own the original and the 2001 editions. Yes, I realized they were the same book. I liked the 2001 cover better.)
A quick trawl through the PW and Booklist databases reveals no previous reviews for the earlier editions of Saints, under that title, though plenty of libraries own copies - well over 300 holdings in WorldCat for the two combined, plus 70 holding libraries for the original Woman of Destiny. So it's not quite the undiscovered gem the review hints at (emphasis on "undiscovered").
Still, six years after its most recent edition, it gets republished, repackaged, and garners a rare starred review from PW. Not bad at all for a historical novel on its fourth life in print.