That's because I think Bishop Sanborn is responding to the original letter of June 9, not this latest interview.  He may not even know about these comments.

Right.  I've made this same point repeatedly.  One can quibble about the precise extent of infallibility, but this is a question of the Church's indefectibility.  To say that an Ecuмenical Council of the Church can lead to the creation of a parallel anti-Church is contrary to the overall indefectibility of the Magisterium and of the Church as a whole.  To say that the Church can promulgate and use a Rite of Mass that displeases God (a Protestantized/paganized Mass as Vigano calls it) and cannot be attended by Catholics in good conscience is contrary to the Church's disciplinary infallibility.

R&R who keep pushing the narrow view of infallibility are missing the forest for the trees.  Sedevacantists often overreact to this error by promoting an extreme view of infallibility that goes too far, when the battle needs to be waged on the level of indefectibility.

I immediately noticed that the logical trajectory of +Vigano's June 9th letter is toward sedevacantism.  Thus far he has held back, instead using the same infallibility argument used by R&R.

Matthew 16:1-3

And there came to him the Pharisees and Sadducees tempting: and they asked him to shew them a sign from heaven.
Et accesserunt ad eum pharisaei et sadducaei tentantes : et rogaverunt eum ut signum de caelo ostenderet eis.

[2] But he answered and said to them: When it is evening, you say, It will be fair weather, for the sky is red.
At ille respondens, ait illis : Facto vespere dicitis : Serenum erit, rubicundum est enim caelum.

[3] And in the morning: Today there will be a storm, for the sky is red and lowering. You know then how to discern the face of the sky: and can you not know the signs of the times?
Et mane : Hodie tempestas, rutilat enim triste caelum.

http://www.drbo.org/drl/chapter/47016.htm

Matthew 24:14-16

And this gospel of the kingdom, shall be preached in the whole world, for a testimony to all nations, and then shall the consummation come.
Et praedicabitur hoc Evangelium regni in universo orbe, in testimonium omnibus gentibus : et tunc veniet consummatio.

[15] When therefore you shall see the abomination of desolation, which was spoken of by Daniel the prophet, standing in the holy place: he that readeth let him understand.
cuм ergo videritis abominationem desolationis, quae dicta est a Daniele propheta, stantem in loco sancto, qui legit, intelligat :

[16] Then they that are in Judea, let them flee to the mountains:
tunc qui in Judaea sunt, fugiant ad montes :

http://www.drbo.org/drl/chapter/47024.htm

I think this is because he was responding to Phil Lawler.  Vigano's writings continue to change depending upon his audience.  I would like to see what he writes a sedevacantist.