This is completely standard, Paizo have always given the rules for free and made you pay for the stories and lore.
It's not even a starter set, it's the playtest, so you already need to be familiar with Pathfinder 2e in order to use the rules. Definitely not a place for a group to test the waters, they're looking for serious dweebs to obsess over the maths and mechanics so they can refine it - the playtest adventure(s) are just playgrounds for them to do that it.
This is completely standard, Paizo have always given the rules for free and made you pay for the stories and lore.
It's not even a starter set, it's the playtest, so you already need to be familiar with Pathfinder 2e in order to use the rules. Definitely not a place for a group to test the waters, they're looking for serious dweebs to obsess over the maths and mechanics so they can refine it - the playtest adventure(s) are just playgrounds for them to do that it.