As far as I know, the only reason for these gentlemen to be Bishops is to provide the sacraments to the faithful.
They are only "sacramental Bishops". The hold no office in the Church, so they are not "to teach" like an ordinary diocesan Bishop would in normal times.
Since Bp. Fellay is no longer Superior General, they three Bishops have no reason to be in the news. Their work is to provide the sacraments, which they have been doing as usual.
This is the way I see it.
Although it is true, as you say, that the SSPX bishops have no office, I’m not sure I would conclude from that that they cannot or should not teach publicly.
if that were the case, then it would apply to every bishop (sede and RR) from the time of Lefebvre until today.
Even the uncensured Vigano would be prohibited, as would all emeritus bishops (eg., Castro de Mayer in the 1970’s).
it would also mean that, during St. Athanasius’s various excommunication, during which he held no office, he was prohibited from teaching.
There is a deeper question lurking here regarding the limits of supplied jurisdiction:
If it is true, as +de Mallerais taught, that supplied jurisdiction springs from the request of the faithful, and these faithful may make such a request for “any just cause” (eg., spiritual benefit), and that this supplied jurisdiction pertains not only to sacramental acts, but to the entire priestly ministry (because jurisdiction is for souls, and not souls for jurisdiction), then why should teaching be prohibited?
Does not the example of Athanasius and others show that Tissier and the old SSPX is correct?
What other explanation is there for Athanasius?
This is my main reason for wanting to translate Dom Adrien Grea’s book on extraordinary manifestations of episcopal power, in the hope it will shed light on this disputed subject.