So if you have an engine out, there will be a maximum of 200 liters that you can't use. About the same as the 139 if you have a boost pump fail.
Not sure what you mean by 200 liters you can't use. There is no situation that you can't use all the fuel in the 139.
The level where it becomes 2 separate fuel tanks in the 139 is 228 Kgs. If you lose a boost pump in AEO mode the engine driven pump can draw all the fuel in the respective side of the system by closing the cross feed. In OEI by opening the cross feed even in a dual boost pump failure (total electrical failure) the operating engine driven fuel pump can draw the fuel from both sides until the total fuel is exhausted.