Loam is a mix of silt, sand and clay, it's mineral soil, it's what is often called 'gold', and is the ideal soil for building sustainable trail out of. What we call loam is duff, which is the soft organic layer that gives that great riding experience, sort of like skiing powder. It's soft, degrades fast, retains water, and is not sustainable in any way.
Why did the incorrect usage of the word even start?