It matters in the sense that the "young-earth creationists" are easily ridiculed and the mountain of evidence against them is strong.
It matters because it's easy, in the soft minds of so many, to represent all creationists as young-earth creationists who believe things that are easily and trivially falsified by geological, astronomical, and nuclear-physics data. So precious few people are willing to do a little reading and learn that in the hundred years prior to the 1960s almost all creationists were ancient-earth creationists, that a handful of charismatic, vocal, wrong religious people are the only reason we even know of such a thing as a young-earth creationist (oh and the idea of a pre-flood canopy of water vapor is frickin impossible as well, and not even Biblical).
If you have ever actually met and talked to a number of atheists, they tend to have a lot of anger and resentment towards established religion and the more nutty followers of it. Some of them even have victim/persecution complexes. They tend to paint with a very broad brush and deny entirely that reasonable spiritual people exist. That would, after all, get in the way of their resentment. I don't believe I have ever met a pro-atheism atheist, but I have met a lot of anti-fundamentalist atheists. The common trait most of them have is that they cannot disagree with something without also trying to destroy it, which could be a lot more effective if they made any attempt to understand why those beliefs arose in the first place.
All of this is readily understood by those who simply want to objectively understand the beliefs in question, both scientific and religious. It tends to be lost upon those whose primary concern is winning converts.