The Penei Yehoshua explains that R’ Yochanan’s ???? was that there were more long-livers in Bavel than in Israel and that within Bavel it was specifically Jews who were living long.
The Ben Yehoyada explains that R’ Yochanan lived for 400 years and his ???? was for sure not about regular old age, rather it was that someone in chutz l’aretz could live as long as him i.e. 400 years.