This is in fact nothing more than the Vatican II ecclesiology, which is just a necessary logical conclusion of EENS-denial.
MAJOR: No salvation outside the Church [dogma]
MINOR: Heretics, Muslims, Jews, "Hindus in Tibet", etc. etc. ... can be saved somehow. [held by most Trads]
CONCLUSION: Heretics, Muslims, Jews, "Hindus in Tibet", etc. etc. can be in the Church somehow. [follows necessarily from the two premises]