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.
At least on my iPhone (no idea if iPads are different) you can reorder, but the icons will always be "dense" meaning no free spaces between them. They will always align in full rows beginning from top left. You can put stuff in folders, and you can change the order, but not have one icon in the third row, without the first and second row being fully populated with icons.