The woman depicted is very likely the target of harassment.

Agreed, but there is no proof of this. We also don't know their true identity to check with them directly.

Sharing the images depicting violence is tantamount to a threat of violence.

The images did not depict violence directly, it was a gory image of a dead person. They were very likely sent by a copycat not involved in the original harassment campaign and intended to fuck up fediverse users more than anything else. They did not appear to imply any kind of threat.

you would have wasted 15 minutes

This would require a lot more than 15 minutes to file a proper report. First we have to collect all relevant information that we have available and compile them in a format that can be submitted. Once we have this information we have to identify a police department to report this to. We are legally based in NL, as that's where our non-profit Fedihosting Foundation is located. I'm based in Germany, so it would also be an option to report it here. The depicted person is claimed to be in Canada, so maybe this should be reported to a police department over there. Or maybe to all of them.

All of this would easily add up to 2 hours or more if you want to do it properly and not just look for 3 online forms to write "hey there is someone sending spam".
If this was a paid job and I was doing this during working hours I wouldn't mind, but all the time I spend here is taken out of my personal time, the same as with anyone else on our team, and also the same you'll see with most other fediverse instances.

perhaps Nicole has been trying to get a restraining order against some creep but has been unable to due to lack of evidence.

If we receive a request for information from (real) law enforcement we'll be more than happy to provide relevant data, but doing this for the (perceived low) chance of that somehow being linked from a random police report is a fairly high time investment as described above.