No, though they are related.
A signal is a costly behavior that predictably correlates with a more difficult to observe attribute. In particular, the cost of performing the behavior normally depends on the attribute(s) in question. For example, it's cheap to tell an interviewer that I'm interested in the job, and can act in a professional manner on the job. Showing up to the interview early and dressed appropriately signals that interest much more effectively, and the interviewer is far more likely to believe the actions than the words as a result. (While you can fake signaling behaviors, it's usually easier to do the behavior when the underlying attribute is present, so they constitute Bayesian evidence. As in all human things, sometimes this works better than others and the details rapidly get complicated.)
A rational astrology is a behavior you do for purposes of societal approval. In general, that behavior would signal a belief in the common beliefs that underlie that behavior. However, the behavior is not done purely for signaling purposes: it's also done to gain the societal safe harbor protection. If you use the normal medical treatment rather than the quack one, society won't blame you if it fails. This reason is often sufficient to justify the behavior, even ignoring all signaling concerns. It also signals belief in the standard medical establishment. The two effects can be somewhat difficult to disentangle.
(You could also take a more signaling-centric explanation of rational astrologies than I did here. You can explain the decision to visit the regular doctor as a signal of caring about your health, as a signal of non-quack-conspiracy-theorist status, as a signal of general social skills, and as a signal of general scientific knowledge. You can then explain the resultant reaction of society as based on reading those signals, not on the rational astrology conformance directly. However, I think this misses something: the character of my condemnation of a known quack who visits a regular doctor will be very different from my condemnation of an otherwise saner person who uses homeopathic medicine for their ailments. I think this is easier to explain given my model above than the completely signaling-centric model.)
I think you're drawing a false distinction here.
First, there's no requirement that signalling be costly. If there were, then "costly signalling" would be a redundancy. We engage in cheap signalling all the time.
Second, a signal given to "gain the societal safe harbor protection" is still signalling. Indeed, this is a common motivation for signalling, displaying signs that tell people "I am one of you, I fit into your community and satisfy the conditions you expect of your in-group."
The article can be found here. While it is not, for many of us, new ground, it is an excellent treatment, and it requires no rationalist background in order to be understood. The subject is the pernicious pull of doing the standard thing, regardless of whether or not the standard thing makes any sense, and it does us the service of giving that phenomenon a descriptive link we can share as well as an excellent name.
I hope to, after more discussion and thought, write a main post on the subject.