You would think that. But as a person having an iPhone... No it is not. At least the part of iPhones currently not having that option.
App-Icons on your "desktop" will always align in dense rows from top left to bottom right, with no free spaces allowed.
It is a bit weird, and I don't really see why, since you can change the order of icons in this dense row-grid. I am glad Apple warms up to the fact that people might actually want some kind of customization on their devices and not everything "the way Apple decrees it".
But to be really honest... I did not even notice prior to this post, and I had all Android before switching to my current iPhone. So at least for me this is a really small non-issue, and maybe a nice-to-have feature.