I'm not 100% sure what Kaplan meant by it, because you're right, Alkaline Phosphatase is expressed on "pre-osteoblasts" and is involved in the laying down of bone matrix. This makes sense since the calcium and such that you need precipitates in alkaline areas, hence the name. Anyway, so alkaline phosphatase is unregulated when the bones are being constructed. Children have higher Alkaline Phosphatase levels than do adults. Likewise, the enzyme can also be high in osteoblastic lesions caused by prostate cancer as well as after a fracture during the healing stages. So in general, higher osteoblast activity/bone formation, the higher Alkaline Phosphatase will be (from a bone perspective, ignoring the role in the biliary tracts for now. That is why there is bone specific and liver specific, you can apparently test for each clinically as they have slightly different properties).
Now, what i'm wondering if Kaplan is talking about here is that sometimes in disease states where there is bone breakdown and then bone formation (Paget's disease for example), Alkaline Phosphatase will be high due to the increased turnover/rebuilding. So perhaps Kaplan was implying that states of increased bone resorption you have increased bone turnover and rebuilding and thus you have higher Alkaline Phosphatase, i'm not sure. Hopefully that is somewhat helpful. Here is a link to an article that has a nice little description of alkaline phosphatase and what it does in the background section (although it sounds like you probably have a pretty good grasp on the standard physiology of it).
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3755844/
