My understanding is that one can download without seeding/uploading; is this inaccurate?

You are correct.

Years ago I did exactly this by modifying my client to never seed/share, and also to fake my reported sharing stats so the private trackers wouldn’t boot me for failing to share.

Those were the days.

Now, I no longer fear the ISP or copyright holder chasing me (seems ISPS and laws moved on where I am) and don’t bother with modifications any more.

> also to fake my reported sharing stats so the private trackers wouldn’t boot me for failing to share.

This would very quickly be identified by private trackers these days because the stats don't line up with your peers and earn you a permaban.

Since the whole system relies on people seeding, even if this may be possible technically, clients don't tend to support it as a feature.

There are some services where you send a torrent file/magnet link and it’ll download the file for you, so you can download over HTTPS. I believe those particular services intentionally don’t reseed.

Correct. E.g., https://github.com/pmoor/bitthief .