Tor is vulnerable to statistical analysis with which if you time it perfectly you can link exit nodes with specific user. [1] The fact that FBI is asking for those specific 35 minutes suggests that they are onto something like this.
Entirely likely, though possibly there are potentially flaws that could allow people to identify it through other means.
I've never used TOR so I didn't realise that this would apply (and it makes perfect sense it would work that way).
It may be that whoever requested the data knows as little about it as I do (or more likely, they know a lot more about what they want and my speculation is completely wrong).
TOR is clunky and slow, it’s not outside the realm of possibility that someone would visit a dodgy forum over TOR, and use their regular browser for other web browsing.
Some sites can be difficult to even access over TOR, especially ones that are very JavaScript heavy or sit behind something like Cloudflare.
[1] https://blog.torproject.org/one-cell-enough-break-tors-anony...