Ok reality is mostly cannon. Cologne has some curse waters in storage at her restaurant because they are useful in both making instant powders and for occasionally making some animals for more exotic dishes on the menu for less cost. But she doesn't tell the Nerima curse victims about it because she also has drowned girl and drowned man water in stock. She doesn't want to have them make the Anthro-mistake. Or in Ranma's case the Hermaphromistake.
After witnessing just how self deluded the Kuno siblings are still not accepting that Male and Female Ranma are a single being at the failed wedding. Even with the individual in hand changing before their eyes. Cologne decides to give them a different perspective.
Cologne ends up cursing Tatewaki with Drowned Girl water and Kodachi with Drowned Man water.
As many have said before its a complete change. Right down to the physical differences and hormones available in the brain.
I could use some suggestions on how the Kuno Siblings should take it. There are allot of perspectives after all and well in the case of Kodachi I don't know the cannon limits of her character well enough to be sure how it would work out. Tatewaki on the other hand I think would be in constant denial even after that time of the month hits or accidental hormonal reactions to guys.