Exactly. I’ll also add that for those states that do not regulate it, you should be well trained anyway. An incorrectly performed test, may lead to inaccurate readings. At best it may cause the expense of an unnecessary mitigation to be performed by the property owners. At worst, it could cause the owners to live in a excessively high level of radon without knowing it.
An ethical inspector WANTS to know what he or she is doing, even if its not required by law.