Before I placed a PCB order with JLCPCB this morning, I realized that some SMD parts (1206 resistors, standard footprint from the system library) which were placed on the bottom layer of my board design do not show up either in the "BottomSolderMaskLayer" nor "BottomPasteMaskLayer". When placed on the top layer, the very same components do have data on their respective solder and paste mask layers on the top.
I had to manually add rectangular areas to the bottom layer to correct this.
Are SMD parts not supposed to be placed on the bottom of a PCB? Is this a known issue or did I miss something?
Brand new interactions and interfaces. 
Easy to use and quick to get started. 
Upon further investigation, it seems that just the Easyeda editor does not show the areas in the solder and paste mask layers correctly. They are still exported to the gerber files.
So, please consider this a bug report.