When creating/editing a Traditional project, you can set a few different geographic fields. Under the Location section, you can set the lat/lon, and you can choose an iNat place from the drop-down (this sets the place_id for the project).
In the Observation Rules section, you can set a place as a requirement for observations for the project (the rule_place).
All of these can be set independently, as can be seen below, where I’ve set the lat/lon to a location in Utah, the iNat place to Canada, and the rule place to Oregon.
Collection projects have a simpler interface that only allows setting the rule place – you can’t set the project lat/lon or the project place_id. As a result, the only way I’ve been able to set a project lat/lon for a Collection project is to create it as a Traditional project and convert it to Collection after setting a lat/lon.
One reason this matters is that the project lat/lon is the information used in the Android app to find nearby projects.
Thus, very few Collection projects ever appear in the Nearby list in the Android app.
Edit: I don’t have access to the iOS app to confirm, but I’m pretty sure this also affects the iOS app.