Your test game is not indexed. And why should it. Read here https://itch.io/docs/creators/quality-guidelines
Your topic is a different question than the text in your posting.
How does itch.io sort games by these criteria: popular, new&popular, top rated, top sellers, most recent?
As far as I know and have observed:
Popular: secret metric of popularity. Horror games are popular on youtube, so they are also popular here. What a surprise.
New & Popular: same as popular, but with added weighting for newer games.
Top rated: weighted metric for the rating average. 1000 ratings with average 4.5 are worth more than 10 ratings with 5.0, this kind of weighting. I do not know the specifics, but a similar or the same system is used in jams.
Top sellers: some metric concerning money. Could be total money spent. Could be individual buyers. Could be anything. But it includes the pay what you want games.
Most recent: Sorted by date. Publishing date, or approved major update devlog.