motherboard – MSI Z370 Pro Carbon Limited to Four USB 2.0 for Front Panel?

I have had this problem for a while now and I have just assumed from my MSI Z370 Pro Carbon spec sheet it can only supply full power to 4 USB 2.0 ports in the front panel. Well my chassis has 2 front 2.0 ports and I have a SD Card Reader in a 5.25 inch expansion bay that has 4 2.0 ports. The 4 2.0 ports on the SD Card Reader are fully powered while the 2.0 Ports on the front of the chassis are in a lower power state and will only accept certain devices. From looking at the spec sheet it clear stays a total of 6 USB 2.0 Ports can be used. 2 on the IO of the motherboard and 4 for the front panel. My question is since my motherboard only supports 4 USB 2.0 ports on the front panel is there a hardware limitation or a hardware problem?

I will provide links to the spec sheet of the motherboard as well as an Amazon link for the SD Card Reader which has a list of specs of the device.

MSI Z370 Pro Carbon Spec Sheet

SD Card Reader Specs