More specifically, it would seem that any mob or entity that has a special effect on death (small snake adds spreading debuff, conflagration exploding) are affected by this. If they are disabled in some way (stun, sleep, etc) they do not properly die.

In the case of conflagration, if it is slept or stunned when the timer expires, it will not explode properly and once it awakes it simply disappears. In the case of the snakes, if stunned before they explode and complete their death animation, they become invulnerable and do not die.