Yes true but not for high end quality speakers which are exactly the ohms tested before retail packaging. i.e. Bose(most) , Dynaudio, Blaupunkt (high end ) FOCAL(these are each individually hand made and each tested !!!).... shall I go on? All of these if it say X=ohms that is exactly what the speaker will be if tested.I have found speaker manufacturers will call anything below 3, "2" in marketing speak.
In car audio you get what you pay for in quality. PERIOD!