Simply, Webster invites the reader to imagine that this one example exists on a spectrum of various levels of “intensity”, but the truth that is waiting to be discovered in the primary sources is that incarnation itself (inclusive of conception, gestation and birth) really is the sole subject and theme being discussed in the presentation of the 12 links. As I’ve said in my earlier essay, in these texts the subject of “birth” (jāti) is extended as far as snakes hatching from eggs, and as far as the supernatural nativity of the gods, but there is absolutely no suggestion that this “birth” is an ontological doctrine of “the interdependence of all phenomena”, nor anything else so abstruse.
In short, the 12 links or “interdependent arising” are only applied to the physical incarnation of a person; this is emphatically not the source of “universal interdependence [of all phenomena]”, which is one of the most popular doctrines of modern Buddhism. The 12 links affirm “no-soul/no-self”, but explicate nothing else.