In my opinion to over water a properly built container it would require the drainage holes to be plugged up. Al

Watering once every three weeks is not overwatering,yet the plant dies because of poor drainage in the soil.

My mothers interpretation:0)

By the way Al, your thought is exactly in harmony with mine.

Mike

meyermike_1micha, my opinion is that overwatering is a soil moisture content that does not allow enough oxygen at the root zone of the plant.
In practice it occurs when water is applied in too much quantity or too frequently. Quantity and frequency are determined by the composition of the growing medium. A clay medium will have less internal drainage than a sandy medium. A plant grown in clay will show the symptoms of over watering quicker than the same species grown in sand, assuming the same regimen of watering.
Plants which tolerate water (anaerobic condition) at the root zone have specialized structures to obtain air.
Swamp rice comes to mind.