Yeah, the way I understand it, Showcase is for things people produced with Typst, be they neat tricks or beautifully-typeset documents. To quote the description from the categories page:
Showcase
This is the place to post in if you want to show off something you created with Typst: Be it the most beautiful paper you have ever seen or something extremely out-of-the box and crazy.
The proposed ‘Package announcements’ category is for a completely different purpose, as described above.