[alisonkisk]

It's not wrong. It's just casually presented and not perfectly precise. the Chapter is about applting geometry in the real world, not idealized mathematical models.

It is standard in empirical science to focus on first order effects, and then to address 2nd-order effects, which the book does in the following pages.

Page 10 is a talking about how the angle of shadow is independent of subject position (human or pole), on the order of ~10m, and so we can treat all shadows at the same moment in time in the local area as similar. (Obviously shadows are not similar when comparing someone in Russia to someone in Mexico at the same time.) This is in contrast to a shadow from a streetlamp, where the angle changes from 45 degrees to 80 degrees over the span of a few meters of relative subject position.

This is true, and the 0.5-degree error due to the size of the sun is not important to the overall result, which is already appromixate to a similar level of precision, and is the same for all subjects.