The thing about Persona 5 not coming to Switch that doesn't track for me even with how strange Atlus is sometimes is that didn't Nintendo choose these DLC characters? Erdrick would make sense (and will make sense) per Dragon Quest XI S, so I'm tempted to view the situation from a binary perspective and reckon that Joker was chosen for similar rationale.
Then again, I'm often the first person cautioning others not to cling to perceived "patterns" in the industry.
Then again, I'm often the first person cautioning others not to cling to perceived "patterns" in the industry.