He comes to the right conclusion, but the αnσnymσus Dominican has the better theology (and is directly on point).
Yes, the Doctor sets up the FACTual information that feeds into the moral considerations. He's correct in pointing out that the SSPX's analysis is based upon false factual premises. It assumes that some great good comes of the vaccine when it's quite the opposite. It typically requires some desired good to offset even material cooperation. You cannot engage in material cooperation in evil merely to commit another evil (taking the jab) ... as it's against the 5th commandment to harm oneself.
It seems that Father Selegny's thinking was that keeping your job is this great good, but if taking the vaccine is an evil, against the 5th commandment, then you can't do it in and of itself. In other words, the evil of the preceding abortion isn't the only consideration, but the evil of the vax itself.