Pope Benedict regrets:

One mishap for me unforeseeable, was the fact that the Williamson case
has superimposed itself on the remission of the excommunication. The
discreet gesture of mercy towards the four bishops ordained validly but
not legitimately, suddenly appeared as something entirely different: as
a disavowal of the reconciliation between Christians and Jews, and
therefore as the revocation of what in this area the Council had
clarified for the way for the Church. The invitation to reconciliation
with an ecclesial group separating itself had thus become the opposite:
an apparent way back behind all the steps of reconciliation between
Christians and Jews which had been made since the Council and which to
make and further had been from the outset a goal of my theological
work. The fact that this superposition of two opposing processes has
occurred and has disturbed for a moment the peace between Christians
and Jews as well as the peace in the Church I can only deeply regret. I
hear that closely following the news available on the internet would
have made it possible to obtain knowledge of the problem in time. I
learn from this that we at the Holy See have to pay more careful
attention to this news source in the future.

Unforeseen, maybe, but unforeseeable? His Holiness–the Vatican II peritus, JPII’s watchdog of orthodoxy–wasn’t aware that the Society of Saint Pius X as a whole had a problem with Nostra Aetate?