They did abide by the signs. They weren’t swimming any more so than sitting by a pool and putting just your feet in. Swimming means submerging in the water. From what I read, they barely had their feet in the edge of the lagoon where it touches the shore.
You are right. I have been at that exact spot many times. It was created to look like a shore line. The toddler was at the water’s edge, with father close by. No one was swimming.
By the grace of God, this wasn’t one of my grandchildren. My daughter and her family live right next to DisneyWorld and have taken many Friday evening strolls right there.