That's incorrect. The old comcast system took congestion into account. I routinely ran 500-600GB/month offsite backups, but I scheduled them for the middle of the night and midday, and I never got a nastygram for exceeding the cap. The new system pretends that all bits are equally expensive, regardless of whether the system is currently slammed or twiddling its thumbs, which is a profit-maximizing lie.
I suspect it was selectively enforced. I had a similar usage pattern and did get a notice.
Pick your poison.
Data cap.
Fully metered.
How is paying for how much you actually use barbaric?
It's actuall the part where you can't not pay for what you don't use. Otherwise it's just stupidly overpriced.