It depends on what you're doing, but for this purpose the Mindsensors motor multliplexer is the device you are looking for - not the port splitter.
A multiplexer (in this context) allows you to independently control/communicate with multiple devices over a single port, one at a time. A motor multiplexer will also need an external power source because a ...
According to this line from the description,
"It also has a pass-through Digital Sensor Port to connect more
sensors/multiplexers. (On this sensor port, you can daisy-chain more
multiplexers to connect additional motors.)"
...you would only need the multiplexer and a power source like the "6-AA Battery Holder with EV3 Mount; Model: BBX003" they have ...