This might seem to be the narrative’s implication, because why else mention such a trivial-seeming detail otherwise? Does that not in fact contradict Gen 1? There are probably a few different ways to make sense of this, but I believe the simplest is simply to point out that from a Biblical point of view the very purpose of the rain and plants is for use (and soon, cultivation) by man; so if there are a few eons that separate the sprouting of the first plants and the creation of man, it hardly matters for the narrative since we are not talking about a scientific explanation but about the origin of man, the tiller of the ground. Indeed, God is himself shortly both to plant and to water the Garden of Eden for Adam, which aptly explains this choice of detail—by contrast with the prior desolation, they relate what a blessing for Adam the Garden was.