Summorum Pontificum says nothing, zilch about SSPX Masses. Neither does Universae ecclesiae. As for Una Voce, they are a good, loyal federation obedient to the Church and her authority and the website you gave reflects that. There isn’t a single mention of SSPX Masses fulfilling one’s obligation or the licitness of their Masses.
As for my source on the liceity of SSPX Masses, the very same site has Pope Benedict’s letter, and in it is this sentence:
The remission of the excommunication was a measure taken in the field of ecclesiastical discipline: the individuals were freed from the burden of conscience constituted by the most serious of ecclesiastical penalties. This disciplinary level needs to be distinguished from the doctrinal level. The fact that the Society of Saint Pius X does not possess a canonical status in the Church is not, in the end, based on disciplinary but on doctrinal reasons. As long as the Society does not have a canonical status in the Church, its ministers do not exercise legitimate ministries in the Church. There needs to be a distinction, then, between the disciplinary level, which deals with individuals as such, and the doctrinal level, at which ministry and institution are involved. In order to make this clear once again: until the doctrinal questions are clarified, the Society has no canonical status in the Church, and** its ministers – even though they have been freed of the ecclesiastical penalty – do not legitimately exercise any ministry in the Church.**
unavoce.org/2009/03/20/benedict-xvis-letter-regarding-remmitting-excomm/
The bolded text makes it clear; that’s the very definition of “illicit.” And because confessions involve the power of jurisdiction, they can’t even validly absolve.
What the site does push for, and rightly so, are the FSSP, and rightly so for the FSSP are in good standing with the Church and you will be hard pressed to find better and holier priests around.