Good points, spaghetti.
Please note that what was quoted from wikipedia was aptly labeled by wikipedia as opinion ("Criticism") on the works and was properly cited as to the source of the viewpoint.
The snippet from wikipedia did not stand alone but was shared primarily because it coincided/matched/meshed with what was posted on the author's own website about successful use with low achieving students.
This seems to also fit with your experience, in using the works with a gifted student younger than the target audience of middle schoolers.
Saying that the books may not be geared for gifted pupils is just another way of expressing that they may not have been written/intended for an audience of gifted pupils.
Some parents of gifted middle schoolers seeking materials for teaching US History may appreciate having this information presented for their consideration in selecting resources.
