Right now, if you die in an SG game to fire damage (fire, fire aspect, lava) or an explosion (tnt), you will enter the spectator mode where you can fly around and noclip through walls, etc. This is generally problematic as you can teleport to other players and track their locations. If you're on a team, you could easily sacrifice a member to lava so they could hunt down other players for you - no bueno. Expected results: When you die to fire/explosion in SG, you should be kicked out to the lobby just like dying to a sword, bow or other typical damage method.
You actually enter spectator mode if you die to anything other than a player. These are the methods I've personally seen lead to spectator mode: Fall damage Fire/Lava damage TNT Drowning Void (not sure if it's possible anymore with the recent map changes to SG1)
Thanks for reporting. I'll see what I can do about this, however the SG plugin is a royal mess, not sure how I'll be able to fix it. I'll do some thinking.
This has now been fixed through a custom solution via one of our plugins. Regardless of the death reason players will always teleport to the lobby on death.