Yes, that's exactly what I said.
If the string in m_ModelName is "models/somemodel.mdl" then you have an entity that is not tied to the bsp, but can be spawned dynamically. But, if m_ModelName is a string such as "*8" or "*17" then it is tied to a brush in the bsp. Trigger_multiple is an example of one entity that is tied to a brush like this.
If you want to create a trigger, you'll have to set one up in code. Set a min/max vector to define an area and then check every 0.X seconds if any players origin is in that area.