At least in the specific case of Herodotus, in his Histories, he has several theories about Greek customs borrowed from other cultures. He also has a relatively open mind about different cultures having customs that are better. For example, he talks at one point how he thinks the Persians (who were often enemies with different city states) have a good custom of raising young children (males) separate from the parents until a certain age so if they should die it is less of a hardship.
Herodotus was fantastic because he was the first historian, but he is seriously lacking as a historian if you judge him by modern standards. That doesn't detract from him as a great man and an intellectual pioneer, but it does mean we should be skeptical of his theories.
For sure, everything he says should be taken with a grain of salt. I was just giving an example of a specific Greek who had some of the ideas the OP was requesting.
