From a purely technical level, the only limit would be how quickly you can get the data in and how quickly you can save it to a storage device. A USB 2.0 hard drive is still going to be faster than the vast majority (if all) Internet connections in Canada as they top out at about 300-400Mbit/s of usable bandwidth after overhead. We don't have Google Fibre, after all.
Limiting to three separate streams has more to do with what they realistically believe is sufficient bandwidth for a home Internet connection to maintain decent quality plus provide enough free bandwidth for Internet usage.
