I really thought it was a myth. I have heard parents talk about using pajames with zippers so that their children can't get into their diapers. Naive little old me always thought, "Gee, can't kids explore their bodies? What's the big deal, Puritans?"
Here's the big deal: There may come a day when your little precious angel is crying during nap time, but you and your devoted husband think she will settle down any second. Well, the seconds will turn into about 10 minutes and you will decide the situation needs some attention.
You will enter Little Precious' room and you will swoon from the stench. You will reach out to grab your little Preciousa/o and you will see that said Angel is covered in poo because the smart, snappy little onsie you bought her was easy to unsnap, allowing for unfettered access to the diaper and all its glory.
It happened. It's not a myth. Sometimes a cry is just a cry; sometimes a cry means, "Mom, I just poo'ed and smeared it all over myself. Can you come here for a sec?"