So basically this. I initially told it to not make my game searchable because it is in a super early state and I wanted it to be a bit more presentable before I allowed people to find it organically. But now I have switched it so it can be found.

I have playtests every now and again and people always report that they can only install it by going to the url directly in the itch.io client browser. It appears that in the itch.io client, it DOES show up in the suggested list.

When searching for it via the site, it does not show up in the list, but it does show up if you actually search for it (press enter).

If your game appears in the results, it's because it's indexed and there are no errors that need to be corrected.

Only the most popular/relevant games are shown in the autocomplete list; if you search, there's a post from the administrator explaining this.