I doubt that the editors of the guidebook are likely to respond here.

To cover the entire universe of Costa Rican hotels and resorts with equal depth would produce a volume so large, demanding such great research costs that none of us would likely be able to afford it, and nobody but the competition would read it all. Further, the costs of constant checking and even visitations to keep the book up-to-date would keep the price too high for buyers. Guidebooks are still useful for getting an unbiased (or almost so) overview of the various regions and popular tourist areas. Much of the specific information that people want is available online for free.

The hotel ratings found on Trip Advisor are both historical and up-to-date and far more useful to someone who can read beyond the stars ratings. Yes, there are some pretty silly complaints in TA and probably a few planted reviews, but they largely replace the guidebooks that provided similar information only a few years back.

The internet and forums like this one also provide much of the basic information that used to be found only in guidebooks a few years ago. It is amazing to me that so many of the questions here are from people who know nothing about Costa Rica and want the denizens of this forum to do the job of a guidebook author and a travel agent. Although, the depth of knowledge here is amazing, we tend to be more limited in our recommendations than the guidebooks.

In response to the specific questions of why this place and not another, I suspect that the editorial staff needed for a really thorough and constant updating is simply not available. I can imagine that hotel owners who work like the devil to be outstanding, and do, in fact, get recognition on Trip Advisor, are probably upset that they appear not even to exist as far as various guidebooks are concerned.