It's not really a problem (as far as I can see at the moment), more an unexpected behavior.
My assumption was that even when particles are present in a tyCache object, unticking particles in the "Enable cache elements" section of the "Elements" rollout of a tyCache object would lead to them not being loaded to begin with. In other words, a tyCache with both boxes unticked would be empty when referenced in a Birth Flow, and when only "Deforming meshes" is ticked, only those would be loaded.
However, it seems like "Elements" might refer to mesh elements, here, so the actual particles are loaded in any case, just without associated shapes or geometry when the box is unticked.
My assumption was that even when particles are present in a tyCache object, unticking particles in the "Enable cache elements" section of the "Elements" rollout of a tyCache object would lead to them not being loaded to begin with. In other words, a tyCache with both boxes unticked would be empty when referenced in a Birth Flow, and when only "Deforming meshes" is ticked, only those would be loaded.
However, it seems like "Elements" might refer to mesh elements, here, so the actual particles are loaded in any case, just without associated shapes or geometry when the box is unticked.