[Chance]

Those are the 5x5 'Stall' lots in public that were previously invisible. It looks like while they were invisible they were being used for decor purposes (no longer necessary since the settlement range covers that space now).

The 5x5 spaces can be used for things like marketplaces now that it's possible to interact with them. If available, you'd just buy it and place down a shopkeeper NPC, then decorate within that space.