Paul was also a Roman citizen. Other "Hellenized Jews" were not citizens and they were not running around persecuting their brothers and sisters, including murdering them, for religious reasons. Paul wasn't just Hellenized, he was decidedly culturally Roman. That citizenship was a pedigree he wore with a certain amount of pride. When you see Paul's misquotes of Torah, it makes you wonder if Paul had any real formal training at all or if he was just twisting the words of Torah on purpose to an illiterate pagan (Gentile) audience.