These are ‘Top’ topics rather than ‘Latest’ and are calculated using this method - Calculating "Top" topics in Discourse
I think your test topic would need to pick up a like or similar to be included, and there’s a background job that runs every hour to recalculate the scores (You can manually trigger it from your /sidekiq/scheduler page if you have access - Jobs::TopRefreshToday and Jobs::TopRefreshOlder for the older ones that runs once a day)
So, from what I understand, the Top Topics section should pull out the topics with the highest score that were created this week.