Chameleon SS includes removing ALL status effects from Enemies. All were removed except mana effect with the three green up arrows. Pics shown of Chamelon special skill description, before Chameleon uses special skill and 2 after, one with MN details.
Sorry but pics start at bottom and then go forward in time as you go back up.
Ludwig has taunt so Chameleon’s remove only took out the Taunt and Special Skill Def Up buffs on him. Once the taunt is removed, the 2nd skill of changing element applies to all enemy heroes
Not a bug as @Liam_K said, special skill effects are applied one by one and in order. At the time of applying the first bullet point, Ludwig had a taunt status effect.