Yes, you have it exactly right. The cable infrastructure was built out in the era of "on demand TV", and the coax cable and frequencies they used required some

Yes, you have it exactly right. The cable infrastructure was built out in the era of "on demand TV", and the coax cable and frequencies they used required some hard choices. Hard in the sense of hardware. Perhaps quite sensibly for the time, they installed hardware filters that allocated most of the spectrum for download.