I understand that ALL DVR expansion ports are disabled on all DVR boxes at this time to maintain copy protection of any programing to external devices.
I have seen conflicting stories about this on the internet. Some people, Satch included, say Spectrum does not allow external storage devices period. The Spectrum link the OP points to is fairly clear saying they are allowed if certain requirements are met. The last group of people say the ports are disabled by default, but can be enabled if you can get to the right tech.
My only advice would be to call Spectrum again and try to get to a higher level of tech. The people that answer the phones are going to take the path of least resistance for themselves, which is to give you the old third party equipment excuse. You will probably have to push back and say it is their box that is the problem, not your equipment. You may even have to be a pest and request a new box and keep at them. If they finally say they don't support external devices than you should tell them to fix their website because it says the opposite. I don't know if doing this will get you external storage, but at least you might get a definitive answer about whether or not it is allowed.
if you do pursue this I would be curious to see what happens.
the E SATA ports are locked on all of the boxes across the board, if it's a big issue there are other providers that allow the use of an external drive.. if there box has a usb thumb drive those are locked across the board also. i imagine the usb ports are just used to reinstall software..
i tried a higher level of tech support. the answer i got was all the e sata and usb ports are locked across the board on all of the boxes
On the Rented Cable Box/DVR provided by Spectrum TV Cable Service, only the internal drive built into the unit must be used for recordings, nothing else.
From time to time, managing the recorded programs (watching them and deleting it when no longer needed) on a weekly basis can free up space for future scheduled recordings. When doing series (recurring) recordings of new (first-run) episodes, for example, I keep the most recent 2 episodes, while older ones after that are auto-deleted as a new one is added. This can solve an issue with the practice of conservation.
if you want to use an external HDD then goto diretv i have the genie with an external 12 TB HDD. or you could get a tivo. spectrum won't let you use an external HDD wich is lame. not saying spectrum does this. but some cable co's have been known to down scale the resolution so they can fit more channels onto there system..