No the thing they are vauge about is the distinction between cannonical schism and the sin of schism.
It's beyond a doubt most sspx advocate schism and to formally cohere with the SSPX you'd be schismatic.
They're vauge about the hypothetical group of people who can go to an SSPX mass and not become schismatic.
Here is some good reading on the subject
https://www.catholicculture.org/culture/library/view.cfm?recnum=1224
https://www.catholicculture.org/culture/library/view.cfm?recnum=1392
http://wdtprs.com/blog/2008/07/guest-contribution-qa-with-the-pont-comm-ecclesia-dei-about-sspx-schism-and-sacraments/
http://www.vatican.va/roman_curia/pontifical_commissions/ecclsdei/documents/hf_jp-ii_motu-proprio_02071988_ecclesia-dei_en.html
The most recent documents make it pretty clear they don't say so openly because it wouldn't be ecunemical/they want to be nice, because they think some might participate in their liturgies without formally participating with their schism, so they don't call it that.
“We declare, say, define, and pronounce that it is absolutely necessary for the salvation of every human creature to be subject to the Roman Pontiff.” (Pope Boniface VIII, the Bull Unam Sanctam, 1302.)
This makes it simple
if they don't submit to the Pope, they are not Catholic.
Also if you look at former sspx groups who rejoined the Church, all the document refer to them as ending their schism.
In addition to this the previously highest canon lawyer on earth whose concern this very issue would be, the head of the Apostolic Signatura, is well rather clear on this.
If anyone should know, it's him, and he's known for being clear and orthodox is all other ways as well.
https://www.churchmilitant.com/news/article/cdl-burke-sspx-in-schism
I don't really know how anyone justifies it to themselves to go it seems… rather clear.
Or well lets look to the SSPX themselves
Why do they say they don't return to Rome?
https://catholicherald.co.uk/news/2018/11/27/doctrine-remains-problem-in-relations-sspx-affirms-after-vatican-meeting/
Because they say they have irreconcilable DOCTRINE with the Pope, they differ from Rome in doctrine to such a degree they don't think they can rejoin, so it's a matter of heresy now as well.
They also maintain that all post 1962 ordinations are probably invalid so we probably don't really have bishops/priests anyway.
They can't be called Catholic in anything meaningful way.
Let's look to a quote from Lefebvre (who signed all the documents at Vat 2.)
>We are not of this religion. We do not accept this new religion. We are of the religion of all time, of the Catholic religion. We are not of that universal religion, as they call it today. It is no longer the Catholic religion. We are not of that liberal, modernist religion that has its worship, its priests, its faith, its catechisms, its Bible."
This is the view of SSPX
They aren't of our religon, that makes it pretty clear.