I might soon regret this, but I'm wading in with a
linguistic point-of-view, not a
theological one
per se:
ut sumamus verbum confuse, id est si intendit facere quod consuevit Ecclesia.
Where "
consuēvit" (from "
consuesc·o, -ere") is an intransitive verb meaning "(she) has been
accustomed", the pronoun referring to "
Ecclesia", meaning the "(One True) Church", used with the infinitive "
facere", meaning "to
do" or "to
perform".
The formula "an intention of doing what the Church does" was used already around the year 1231 by Gulielmus Altissiodorensis who explains it in this way saying: "that we take the word confusedly, that is, if he intends to do what the Church is wont to do."[**]
Perhaps there are some readers who've been misled by the crucial word "
wont", by assuming that it's some strongly conjugated tense of "
to want" in quaint English, expressing "want" in its sense of internal or mental
desire, i.e., loosely the modern-English meaning of "
intention".  But it's
not!  Instead, the crucial word is an adjective and weakly conjugated verb meaning "
to be accustomed".
So that clarifies the English to a more readily understood meaning:
"[...] if he intends to do what the Church is accustomed to doing."
Or more loosely, "[...] what the Church
usually does."  Not "wants"; not "desires".
It seems to me that the adverb "
confūsē" does not refer to the hypothetical heretic or pagan amateur
baptist, but to the "
we" of potentially
confused theologian readers of the multivolume work
-------
Note *: Cited (in <#p86>) above as
Sacrae Theologiae Summa - De Sacramentis  Vol 4, P. Josepho de Aldama S.J., BAC,
[i.e.: Biblioteca de Auctores Cristianos: (Madrid?) Spain], 1962. p. 76.
Note **: Cited (in <#p86>) above as
Sacrae Theologiae Summa - On the Sacraments in General  Vol. 7
[a.k.a. "4-A"], Rev. Kenneth Baker S.J. trans., Keep The Faith
[Inc.], 2015. p. 87.
Note #: Publication in 8-vol. translation to English announced at least as early as 2016: <
http://novusordowatch.org/2016/08/sacrae-theologiae-summa-dogmatic-theology/>.