Any mobo fan header can deal with the speed signal sent back to it from only ONE fan. So when you use a Splitter or a Hub, it will send to the host header the speed of only ONE of its fans and ignore all the rest. On your Hub, the single output port that is marked specially is the ONLY one that will send its speed signal to the header. But that does NOT make it the fan in control of others.
All fan speed control is done by the header via the signals it sends out. When you use a Hub, ALL of its fans gets exactly the same signals. If they are all the same fan model, they all will do exactly the same thing.
There are two widely-used fan designs. The older design uses a 3-pin connector and its speed is controlled by supplying to it a voltage on Pin #2 that can vary from 12 VDC (full speed) down to about 5 VDC (minimum speed without stalling). The newer design is controlled differently and uses 4 pins. Its power supply from Pin #2 is always the full 12 VDC. It also receives from the new Pin #4 the PWM signal, and it has a special chip in the motor to use that signal to modify the flow of current from the 12 VDC supply line though the windings to change fan speed. Because the METHOD of controlling motor speed is different between these two, it is best not to mix them in one circuit.
If you connect a 3-pin fan to a 3-pin header (or even to a 4-pin header set to use the older Voltage Control Mode), its speed can be controlled with that method. Similarly, if you connect a 4-pin fan to a header using the new PWM Mode, its speed will be controlled. But if you plug a 3-pin fan into a header using the new PWM Mode, that fan will always run full speed. It receives from Pin #2 the constant 12 VDC supply, and it has no way to use the PWM signal from Pin #4 to change that.
The fan Hub you have from Arctic is designed the same as almost all others: it gets the 12 VDC power its fans need from the PSU and sends that out to them all, and it gets the PWM control signal from the mobo header and sends that pout to all its fans. Thus it provides output ports for ALL of its fans that always act as 4-pin headers using the new PWM Mode. IF you plug any 3-pin fan into its ports, that fan can only run at full speed all the time (as above). Note that the mobo header in use here MUST be configured to use the new PWM Mode so that the Hub can send that out to its fans.
So, look at those fans you bought - you have not told us which model. IF the connectors on the ends of their cables has THREE holes, then you cannot control their speeds using that Hub. In that case you would need to change all the fans to 4-pin models, or perhaps to get a different Hub - there are a very few that can deal with that situation. If you need details, post back here.