I'm not even certain though if the author of the article Ivan Gobry is a priest. I'm think he is simply a layman. Either way, he would be of the SSPX position.
Actually, this piece of information is VERY important. If he is not a priest, then he is not even in the SSPX, because the SSPX is a priestly society. And being a layman who attends their Masses doesn't mean that the person speaks for the SSPX.
I am reminded of this movie about St. Thomas Moore, where one of his servants says, "we're all on your side, you know that", and St. Thomas says, "what side is that" and the servant says (in so many words) "Oh, come on now... we know what you think!" And St. Thomas sharply rebukes him, saying, "None of you knows what I think, and if you guess at what I think and spread it about, you do me no good service!"
Unless you are one of the four Bishops of the SSPX, then you really cannot speak of what the SSPX thinks "infallibly" because you are not at it's head deciding what it thinks and teaching it. Even their priests can say something that they THINK, and it may absolutely not be the position of the SSPX. There is an important difference. Just as one churchman can say what he thinks, and that does not mean it is the teaching of the Church.
It seems like a trifling detail, but we all have to remember: even the members of an organization may speak something which that organization does not approve of. And we do an organization an injustice when we take what one of it's members say, and without confirmation, spout it off as being what the whole group believes.
One day, I think, the Catholics of the world may shed their blood for (dangerous) indifference on this very point. Just picture the media quoting some lunatic who calls himself Catholic, who wants to go out and kill Jєωs or something, and saying that's what WE all think!
It would be a very ironic error indeed for us, then, to go around doing this same unjust thing to others, that one day we may be imprisoned or even die for.