We personally know a so-called bishop of this group. Fr. Pulvemacher, directed this married man to this group to be ordained a priest. Then he was made a bishop to elect Pope Michael I. This Durate Costa group was excommunicated by Pope XI. Note
this group well, they are around. The one we know is in the Phoenix area. The Trads have shown he and his wife the door of the church, to leave. Note that they also only go for group absolution not the regular confession. They are a dangerous bunch!
It's a nitpick, but I'm sure you're referring to Pope Pius XII.
And got to ask, are you referring to Fr Carl Pulvermacher, or his brother, Fr Lucian "Pope Pius XIII" Pulvermacher? Though I wouldn't have embraced his movement, I always felt a kind of sympathy for the latter, came across as a kind, guileless man, and his writings were perfectly orthodox and traditional.
Also, if you're referring to the absolution after the
Confiteor in the TLM, that is not sacramental absolution, and in and of itself, cannot forgive mortal sin. There is no "group absolution" in traditional Catholicism (aside from a rare crisis situation where absolution has to be conferred quickly to a group, such as impending death in warfare).