It's like being a little bit pregnant. Semantics of advertising based on capitalism.As DNewton is fond of pointing out, there is no such thing as a totally "true synthetic" off the shelf motor oil. All of them are a mix of "true" synthetic with some Group III or Group II in the mix to varying percentages. Or a straight Group III.
Only a few folks seem to be worked up by that. Modern Group III comes darn close to Group IV performance and even has some characteristics that are better than Group IV. The average auto owner would see no difference between them and the result in their engine.
It is legal and not false advertising to label Group III as synthetic. All the legal hurdles were scaled many years ago. Only the purists hang on.