Should little kids sit with their legs splayed back in a "W"?

You know how babies first start to sit on their own, they bend their knees so their feet are behind them, but they aren’t sitting on their legs, their legs are sort of next to their bodies. My 3 year old still sits this way and his preschool teacher said sometimes this causes problems with their gate and that we might want to encourage him to sit with his legs in front of him. I suppose I’ll ask our pediatrician about it, but we haven’t seen any problems in his movement, has anyone heard of this? Is it a problem with some evidence behind it, or just the latest thing to worry about?