because any occurance like that would go like this
Tsunade: Summoning jutsu!
Katsuyu: I am here lady Tsunade.
Madara: *Slices Tsunade and Katsuyu in halve with PS*
One does not simply slice katsuyu
Katsuyu can be contained as she can change shape and form, and she is immune for physical attacks, she can even tank to 8th gate databook says so
Tsunade had a mysterious hand seal towards the end of the fight but she was going to use all of her chakra on katsuyu because she wasn't at her peak , tsunade just got out of acoma, katsuyu would have to use the Byakugou seal , acid would count as senjutsu so k doubt madara would absorb it ,