Each folder inside the zip file contains both the files and another zip file containing duplicates of the files.
Unpacking the nested zips, asking a duplicate file finder to delete all but one copy of each duplicate file, and then repacking the archive drops the download size from 249.2MiB to 124.6MiB with no lost content.
Given how easy it is to turn a folder into a Zip file, probably a good idea to treat that as a mistake and save people the bandwidth. I can’t imagine Itch.io gets unlimited flat-rate bandwidth, and I know not everyone has flat-rate bandwidth at home.
(American companies like to gouge people, incumbents here in Canada like to gouge people, people who have to connect through a mobile dongle won’t get flat-rate bandwidth, and the best option you could get in Australia last I checked was to drop to dial-up speeds rather than getting charged when your monthly bandwidth runs out. As I understand it, big enough companies partner with Australian ISPs to set up mirrors in Australia which are exempt from bandwidth caps. I’m guessing New Zealand is similar, given they’re Australia but even further as far as undersea cables go.)