Bruh.. i think you choose wrong argument here. In this panel it clearly stated higher dimension and not only that it show a picture of tesseract, it mean 4D space are exist in OPM verse
Because 4D space are exist it clearly mean the entire cosmology are 5D because 4D space and 1D time
And this is not something like a 2C, 2B, or 2A space that being a "higher dimension" just because it contain universes, it not entirely higher D since it not have higher D volume just axis. In OPM, the space clearly stated as 4D, it mean the entirety of that space are 4D by default, it showed tessaract mean it not just 4D in axis but also 4D in volume. So that space are significant