Hi kynfs,
I don't usually offer advice as that's not my role here, but as it relates to the intent of our guidebooks, I find AI to be spot on. S/he is correct that our books are not meant to be comprehensive. I think this is meant to be a positive thing in that you should consider getting off Rick's beaten path. Our books are opinionated about what Rick thinks are your best options for multi-week trips. There can be many reasons why a site isn't listed in his books.
The first -- as you've already divined as an option -- is Rick doesn't like it. Second is it may not be well suited to a certain volume of visitors that a guidebook's recommendation can send to any given place. Third, it may be out of the way. Fourth, there may be another suitable/comparable option already in the guidebook and we are avoiding making as if you should see both on one trip.
However, this doesn't mean it isn't a good site and worth the time for you. It sounds like you've found a site that you're interested in, so you should go! It looks like you have the latter part of the day free on day 7 of your tour, and you should ask your guide on the first day of the tour about taking this side trip. S/he can help you plan it and give advice too.
Perhaps someone else who has taken this tour can speak to opportunities to see windmills in action during the tour.