Even if you computer is not exposed to the internet: are you certain that every other device on the network is safe (even on public wifi)? Would you immediately raise the alarm if you saw a second printer in the list with the same name, or something like “Print to file”? I think I personally could fall for that under the right circumstances.

Is this a threat?

With this approach you would lose the subvolume structure and deduplication if I’m not mistaken.

The most common physical attacks will be you misplacing your device or some friend/burglar/cop taking it. FDE works great in those scenarios.