That doesn't prohibit modifying the device with such parameters, this prohibits having devices that are even able to be modified, and a device that is merely able to be modified, period, is able to be modified with such parameters.
That actual term is "properly authenticated software". That doesn't mean the firmware can't be modified. It means a method must exist that authenticate the firmware executed on the device. You are implying that it means no modification is allowed, but the FCC purposely waved their hands on the details of who or how the firmware can be authenticated with "the manufacturers may consider applying existing industry standards for strong security and authentication."