Well, the important distinction here is between EENS and between BoD. Where the Dimonds cross the line is in declaring any belief in BoD, even if it's the version held by St. Thomas, St. Alphonsus, and St. Robert Bellarmine to be heretical. I don't believe in BoD and I disagree with these saints, but to hold that the Church declared Doctors of the Church three men who taught heresy is too much of a stretch. In fact, it's clear that the Church has long tolerated a belief in a Baptism of Desire. But, contrary to what the BoD theorists hold, it's equally clear that the Church has never defined anything about BoD, nor can the Church positively defined a BoD, since it's obviously rooted in nothing more than sheer speculation. There's no evidence whatsoever that BoD is part of the Deposit of Revelation.
With that said, however, a belief in a BoD for those catechumens or catechumen-like souls who actually have accepted the Catholic faith and intend to become Catholic is not fatal to EENS. What's fatal to EENS is when BoD gets extended to those who have nothing even resembling the Catholic faith, to anyone of sincerity and "good will". St. Thomas, St. Alphonsus, and St. Robert Bellarmine taught no such thing, but the BoD proponents constantly imply that they did.
In any case, when the Dimonds denounce as heretics those who hold even a very limited notion of BoD, they cross the line into schism, because they consider to be outside the Church those whom the Church never has.