so the marketing will not be in vain
How do you think marketing works? You advertise your project and people go running to Itch and type your projects name into the search box?
If you actually market your project, you will do so by posting a direct link. A direct link does not care about indexing.
Seeing how all your 17 projects are indexed, why do you even worry. Also, what hechelion pointed out. They do not do reviews on all new projects. So there can not be a pre-review. Possibly all factors will be considered, when the automatic decides what will be indexed and what will be staff reviewed.
Projects can also be put again on review after an update. So releasing a placeholder, or in development version and later updating it to the finished thing is also not a sure way to get indexed and stay indexed.