Someone called Fr. Pfeiffer, and regarding the charges against Fr. Tetherow, Fr. Pfeiffer said, "All lies. None of it's true."
...Just like he said about Ambrose Moran.
History repeats itself.
So yes, he's aware of it.
But even if someone didn't tell me personally that he called Fr. Pfeiffer and asked him about it, I'd guess Fr. Pfeiffer knows, because it's on CathInfo for crying out loud!
Everyone that "matters" in the SSPX and Resistance either reads CathInfo, or has someone keep an eye on it for them -- even if I do say so myself.
Let's be realistic. There is no larger or more popular forum for this topic (Trad Catholicism, the Resistance) than CathInfo.