The graphs describe that earphone, as it is equipped to that coupler. It does not describe things like manufacturing tolerances, or defective samples.
The coupler is a standard coupler and can be reasonably compared to other couplers of similar type.
The measurement can be altered by a different fit, a loss of seal, a change in insertion depth, a different tip, and so on. These changes, if the condition is reproduced, can be detected by the listener as well.
It may not...