I have been pretty much convinced that OU DIKAIWQHSETAI PASA SARX, should be understood as “No one is justified” rather than as “Everyone is not justified (some are).” And that the expression was generally how the idea that “absolutely no one” would be emphatically expressed in Greek idiom.
I was reading in David DeSilva this morning, and found this
“that basis (the basis for the universality of the Gospel message) is not Torah, the observance of which had functioned to keep Jew separate from Gentile for a limited time, for “all flesh shall not be justified by works of law” which only pertains to Israel.”
He seems to understand OU DIKAIWQHSETAI PASA SARX as meaning “Everyone is not justified,” that Torah had brought about two classes of people. Under Torah and not under Torah.
Leaving theology aside, which is the better way to understand the Greek expression linguistically.