Who knows, some people seem to be afraid of water (which plants need). That really isn't a great pic to make such a determination anyways.
Overwatering is really from lack of oxygen, which roots need. Water can only hold so much oxygen, so if your plants are soaked all the time it could happen. Also bad media that doesn't drain good or has poor air/water ratio can exacerbate the issue. Good rule of thumb is to use the container weight to help you determine when to water. Potting mix should always be somewhat moist (never bone dry), but after you water completely the container will be much heavier.
If you're watering every 3 or whatever days, depending on container size you shouldn't have any issues with overwatering using good potting mix/soil. Plants will always need to be watered less frequently following transplants. As roots grow in you'll probably need to water more frequently.