Yeah, I don't get what people aren't getting. Anything not "in your library" doesn't appear in the desktop client. Which is why it is so baffling they haven't provided proper support to get it all in there. Until it goes in your library, it's like you didn't buy it as far as any integrations and clients are concerned.
FYI, in that same reddit there is a tampermonkey script that will go through the bundle and add everything to your account for you. The first version did it instantly and submitted hundreds of requests a second, which was problematic so itch asked people not to do that. There's an updated version that waits 2 seconds between each request, so it takes forever but gets you the functionality itch should've provided themselves without DDOSing itch's services. You just have to leave a tab open in the background cause it will literally take a couple days to do it for you at 2 seconds per request lol.