Natural selection operates at different speeds under different circumstances. Scientists agree that natural selection over long periods of time can produce larger evolutionary change than natural selection can produce in shorter periods, but exactly how much more is a subject of ongoing research.
Explore Evolution claims that there are inherent limits to the amount of change that evolutionary processes can produce, and that these limits make it improper to extrapolate from short-term research on natural selection in explaining the long-term evolutionary change we see in the fossil record. Alas, their argument for inherent limits to evolutionary change is rooted in exactly the sort of fallacious extrapolation they decry. The work scientists do bears little, if any, resemblance to these sorts of erroneous extrapolation.
To illustrate the claim of improper extrapolation, Explore Evolution actually invents data from whole cloth, presenting a graph of finch beak size "extrapolation" vs. "data" which is actually contradicted by the data obtained from field research. Where the text and graph suggest constant oscillations within fixed limits, research on the Gal pagos finches show directional change in beak shape in addition to cyclical changes in beak size. Furthermore, those cycles match the cyclical environment the birds live in, so it is inappropriate to treat those oscillations as inherent limits to the birds' evolutionary capacity, rather than a reflection of their ability to rapidly adapt to large environmental changes with equally large evolutionary change.
As always, Explore Evolution passes up any opportunity to give students the data or opportunity to propose their own tests of any of these claims, belying the book's claim to be inquiry-based. Students are expected to learn by rote that limits exist on evolutionary change. They are never told how researchers actually investigate the ways in which various factors do limit evolutionary change.