Yeah, but no Doctor or Church Father or Pope ever taught a form of BoD that would allow infidels to be saved. They believed in BoD as efficacious only for those who were Catholic in every other way except for the in re reception of the Sacrament. That's the distinction I always make.
If someone believes in BoD as St. Thomas did, I personally would not even characterize that as an "error". I would disagree and think it a mistaken piece of speculative theology.
By their approval of beliefs that allowed people outside of the Church to be saved, they opened the gates for modern clergymen to fling open the gates to all infidels. Now we're stuck with the V2 Popes saying "It doesn't matter if one is Catholic".
The belief that Jews, Muslims, etc. can be saved is certainly heresy, but the failure of pre-V2 Popes to condemn it while it was running rampant among the clergy, and the support given to it by post-V2 Popes, means that a Catholic who believes it probably thinks that's what the Church teaches. So it probably isn't a formal heresy in most cases.