No, you're thinking about USB-A to USB-A, which is definitely prohibited by the spec. (Whereas USB-C to USB-C cables are most certainly not disallowed.)
What's disallowed is for a non-host to have USB-A, hence, USB-A to USB-A is impossible, because one side of the cable has to be connected to a "device" that's not acting in host mode.
Only the host is allowed to have USB-A.
This is exactly why USB-A is superior to USB-C for host-only ports on embedded devices like routers (as well as auxiliary USB ports on your desktop or monitor).
Generally, many modern travel routers have one USB-C and one USB-A port. Without any documentation or pictograms, you can be relatively sure that USB-A would be used for data, and USB-C is for power (hopefully, through USB-PD). Since USB-A couldn't possibly be used to power up the router, since USB-A is a host-only port.
USB-C is great for USB-OTG and the bidirectional modes, when the same port could be used for both the host and the peripheral device functions, like on the smartphones. https://en.wikipedia.org/wiki/USB_On-The-Go
If the port can ONLY be used in host-mode, and does NOT support Alt Mode, Thunderbolt, or bidirectional USB-PD, then USB-A is a far more fitting connector, to signify all of the above.
What's disallowed is for a non-host to have USB-A, hence, USB-A to USB-A is impossible, because one side of the cable has to be connected to a "device" that's not acting in host mode.
Only the host is allowed to have USB-A.
This is exactly why USB-A is superior to USB-C for host-only ports on embedded devices like routers (as well as auxiliary USB ports on your desktop or monitor).
Generally, many modern travel routers have one USB-C and one USB-A port. Without any documentation or pictograms, you can be relatively sure that USB-A would be used for data, and USB-C is for power (hopefully, through USB-PD). Since USB-A couldn't possibly be used to power up the router, since USB-A is a host-only port.
USB-C is great for USB-OTG and the bidirectional modes, when the same port could be used for both the host and the peripheral device functions, like on the smartphones. https://en.wikipedia.org/wiki/USB_On-The-Go
If the port can ONLY be used in host-mode, and does NOT support Alt Mode, Thunderbolt, or bidirectional USB-PD, then USB-A is a far more fitting connector, to signify all of the above.