I understand this is frustrating so I decided to try and help(not sure if this is helpful but I hope its a start). This issue in particular is one I have seen only some people have a problem with. I downloaded several games from Itch io that didn't have this issue which made me suspect there was a workaround. I spent some time researching and it seems this is actually an issue with .zip compression. Im not a developer so I cant help too much but here is what I found. https://stackoverflow.com/questions/107903/how-to-create-a-zip-file-in-the-same-format-as-the-finders-compress-menu-item
the other solution I heard is to use .TAR https://github.com/golang/go/issues/24057
the comments on this thread are quite informative
It seems that macs default zip compression does not properly store metadata so you need to use the [ditto] command
I also found this although you probably already read it https://itch.io/docs/itch/integrating/compatibility-policy.html
I hope that helped some :)