The first sentence of the new book Tests of Astrology by Dean, Mather, Nias, and Smit reads "Astrology supposes a link between the heavens and human affairs." This statement is factually inaccurate and results in a plethora of misconceptions that follow.
The term "supposes" is not the problem, but the term "link" cries out because it makes astrology seem like 18th-19th century physics. I do not believe astrologers today accept that there is any measurable physical influence that accounts for astrology, as this definition suggests. By framing astrology within a causal definition of links, Dean et al set up a straw man that they can easily attack.
The term "suppose" does not need to lead to any causal relationships. For example, in multi-universe theory we can suppose that our universe has a "relationship" or is "relative" to parallel universes where choices made in this universe were made differently in another. Choices in one universe do not cause choices in the other and yet a relationship exists. Nor does a "choice point" need to cause a split or a specific outcome in any particular case.
If astrology has rules, based on a corpus of observations, for finding and mapping choice points and potential outcomes, the rules could be heuristic or they could describe causality. Dean et al provide no justification why astrological rules need to be presumed causal.