The Split Two Columns block doesn't use an srcset for all images, even though we always have that available. Additionally it uses the original image, which can be of any dimensions (i.e. potentially adding megabytes of data) EDIT: it's actually capped at 2500 width, but that can still be really large

e.g. https://www.greenpeace.org/sweden/agera/boka-en-greenspeaker/