First, I don't think the oil is hot enough for frying. On page 11 at tomshardware.com it says they were at 40°C (104°F) and that's just not hot enough for deep fat frying.
As for the oil moving, it doesn't need to. The oil is a poor electrical conductor, but an excellent heat conductor. The heat from the hottest components will raise the temperature of all the oil, eventually. Still, adding a pump to make the oil circulate would probably help draw the heat away from the hottest components faster.
Finally, on the life expectancy of such a system I have no idea. The hot oil might start corrosion or dissolving some parts of the system. Or, maybe it would remain chemically inert and increase the life of the submerged components. Someone would have to run on oil cooling for several months then drain it and check the board for chemical reactions. Only time will tell.