Using moduleName.propertyName vs this.propertyName

In the modules exercise, the object we create to represent the module uses the following syntax

const objName = {
  firstPropertyName: firstValue,

 firstMethodName: function() {
   console.log(`The first property's value is ${objName.firstPropertyName}`)
  }
}

In previous exercises we were taught to that referencing a property within the same object we should use the “this” keyword. So how come in this exercise to reference a property (or method) within the object we use the objects name, i.e. why are we referencing objName.firstPropertyName instead of this.firstPropertyName?

this is within the Workaround Project

Thanks