This includes attacking mobs that are "in stasis" because no player is close enough for them to be active. The main pet shroom will simply nuke down mobs that do not move or attack, the animist can practically afk farm with just the main pet as long as no player gets close to the shroom.
I just encountered this behavior when farming XP and I had to afk, ran away so I would not die when the shrooms go down and came back to my main pet happily attacking way out of my clipping range.
