Ah yes, I have seen it.
But that addresses a reality, not an assumption of intelligence or inherent trustworthiness. If the situation is such that today they clearly are makpid, then they can be bodek. And be believed, because now you have b’yado, I imagine. So its purely a practical question, and if the halacha is based on the facts which may change – no big deal. ‘Halacha’ isn’t adapting to new understandings. He was claiming that certain assumptions were once made (read: which are now understood to be false), based on social understanding, not circumstantial fact.
Of course lets not forget that the Mishne Brurah observed the same, and did not change the psak.