Different versions of Windows and Linux.
Short description of error
A mesh, set as outflow, doesn't remove the secondary fluid mesh generated by the Fluid Particles option. Tested with different volume initialization options and different meshes, no difference. I even put a secondary outflow mesh (the plane, rendered in wireframe) just beneath the the first, rock-like mesh... I thought maybe the first mesh doesn't work properly; that didn't help. Those water blobs just go through and hit the domain's boundary.
My detailed question on blender.stackexchange
Exact steps for others to reproduce the error
Create a fluid simulation with (as in my case) an inflow mesh, a domain set to Fluid Boundary -> Subdivision: 3; Fluid Particles -> Tracer: 100 Generate: 1. Then put an outflow mesh in the way of the simulated mesh (fluid) and you'll see some mesh particles go through not being terminated at the contact with the outflow object.