Hi Rae - welcome! You really only need to worry about this with larger tiers - say 12” diameter or larger. The heating core or flower hail helps the center of the batter bake faster. I personally prefer an upside down flower nail for several reasons… a) nails make a very small hole which completely disappears after you ice the cake, b) I find the batter rises way too much and bubbles out of the heating core, c) the cake “plug” from the heating core has to be trimmed and leveled to fit in the baked layer, and d) the cake baked in the heating core tends to over bake so that it’s darker in color and dryer than the rest of the layer.
There has been lots of discussion about this here on the forum, and on the blog - just do a search and you’ll get lots of info on the subject.