The metadata was or probably still is being collected from the notifications on the phone. So while Signal itself didn’t leak data the notification popup was. The sender wouldn’t have a popup, but the receiver might. Thus sending to the reporter vs receiving from the reporter would matter.
1. Feed cat, ensure that friend will adopt cat.
2. Talk to any family members.
3. Uninstall Signal
4. Take too many Ambien.
Or:
“I’m sending this to you confidentially so please don’t respond since metadata will show I contacted you.”
Reporter: responds anyway