It's displaying all materials for every row which leads to the page becoming far too wide, also it's displaying a row for every page that you add to the summary, which leads to the whole thing also becoming far too tall when adding lots of pages. The legacy page fixes this by only displaying materials that you have selected, and also hiding pages that do not have the selected material or materials at all.
Requested by @XhenZui in https://github.com/have-fun-was-taken/yafc-ce/issues/159#issuecomment-2182573695: