Is a toddler wearing a shirt and a diaper inappropriate?

Over the weekend my wife snapped a few pictures of our 22mo running around splashing in a lake wearing nothing except a shirt and a swim diaper. My wife was quite taken aback when she uploaded the photo to Facebook, and had the picture removed for nudity / inappropriate content. We all rolled our eyes and figured this was just an overtrained AI being an overtrained AI, but it's got me wondering - is this attire getting to the point at this age where it really is inappropriate, and I'm just too fuzzed out from taking care of babies to notice? Curious to hear ya'lls thoughts.