Cleaning yourself

So I have a friend who is working on her Masters to become a PA

We were talking the other day and she mentioned that she doesn’t use any soap when cleaning her lady bits. She said that ANY kind of soap (even summers eve)

can throw off your Ph?! Is this really a thing? I mean, I was told not to use soap when washing postpartum, but I didn’t know you weren’t really EVER supposed to use any kind of soap...??