They could put cartoon images of "land", like this TV show's overlay on top of a lady wearing Muslim dress: https://youtu.be/17oCQakzIl8?t=270
Interesting how the IMO Chinese "Eh, imma just half-ass it!" mentality (hopefully having visited the country and experienced half-assery, I'm allowed to comment) basically lead to this research work.
The scale was definitely a problem. The article talked about how they had millions of blanked out areas, anything of even the most minor strategic importance was blanked out. It might even be an attempt to stymie this kind of investigation by making the data too noisy.
They definitely screwed up when they made the censoring so easy to spot.