TL;DR: I get “bronze” rewards for Jade Cannon events even though I’m on the other side of the map and definitely didn’t tag any mobs or participate in any other way.
When I go to Lake Doric, I start by going south and getting the first heart by training with the militia, then pick up jade fragments in the south and the middle of the map. Most of the time I don’t attack or kill anything except the training NPCs by this point. This is when I usually get a popup informing me that I have successfully participated in a Jade Cannon destruction event. First two times it was the Fort Evennia cannon (I could tell by the tick next to the daily achievement). I haven’t even been close to it both times. Today it’s Saidra’s Haven cannon. I passed by it but didn’t engage any mobs (and my Engi doesn’t have passive attacks or offensive triggers of any sort).
So yea, I’m absolutely 100% positive that I didn’t participate in those events.