Citystrides takes the data about streets and nodes from OpenStreetMap (OSM) and applies a filter to determine which ones should be included as runnable in CS. Since OSM is a collaborative project there isn’t 100% consistency in the way different areas are modeled. It’s possible that someone gave the cemetery roads in Marple Township an access tag that has them included, whereas that tag is not present for those in the cities you already completed.
The good news is that since OSM is a collaborative platform you can go fix stuff that’s incorrect yourself. For example, adding a gate and setting access to private is pretty straightforward (for more detail see here). Changes you make in OSM will be reflected in CS when the city is updated (happens roughly every 4-6 weeks).