Correct, using Tor has a chilling effect, just like using cryptography used to have. Hidden in plain sight and blending in crowd is not foolproof either. If you don't do anything wrong on Tor, you're noise. However, some signal on Tor is information I find unethical (e.g. pedophile and terrorist content). If I want such distributors to be busted, lowering Tor noise seems to be in my interest.
Its like if I were an analyst at a national security TLA, I’d treat TOR traffic as a big red “look at me!!!” flashing light. Sure, you _might_ be using TOR to anonymously report a pot hole to your local authorities, but you’re _way_ more likely than average to be doing something the government has “a war on”. (So as an analyst I’d assume you’re involved in drugs, terrorism, child abuse, or insisting on government accountability.)
You probably don’t want “a library of garbage”, you probably want something a little smarter that breaks all your traffic into totally plausible “normal looking” traffic but with each stream (browser tab/website pair I guess in this context) looking like a different but totally “normal” session. So your HN session looks like a totally stock Win10 Edge browser session, but when you click over to (or open a tab to) eff.org, it changes to maybe a SamsungS20 session, and when you flip somewhere like NYT - all the page loads and the hundreds of tracking pixels all see what looks like a macOS Safari session.
Do-able, I think, but more complex that simple “garbage” traffic. Needs stateful session inspection so it could do things like stripping referred headers when you change top level sites/urls, while sending them normally to image/xhr/tracking URL calls from within a site.