Well, at least it doesn't actually explode twice. I'll look into it though, might be something funny bunny with Snuff Out? As deaths go, Snuff Out is a weird way to go. Thanks for the report!
I encountered the double message too in every summoner encounter. (I thought it was a feature to make the player feel extra rewarded for surviving so I didn't report it.)
In the 7/1 build, in addition to the double relic explosion messages, I just saw a double death message on a single ukobach that died due to ignite during a link (see the "(x2)"):