So the question is, can I substitute the 2 resistors by only one of these?
No -- the four-terminal shunt resistors you've found are still only individual resistors, so you'd still need two of them. The extra pair of terminals are your sense connection -- you pass the current through the 'outer' pair of terminals, and read the voltage drop across the 'inner' pair. That way you measure the real voltage drop across the resistor, instead of the combined voltage drop across the resistor and the current-carrying connections to it; the technique is called four-wire (or Kelvin) measurement.
(ETA: as, in fact, mentioned in the datasheet you linked!)