Interesting. Even priests don’t seem to differentiate, considering the number of “convalidation” entries you find in registers where you know the marriages being “convalidated” were those of Catholics married outside the Church (because that marriage is noted in the register) where there was no presumption of validity.
Which also brings up the question, how then can you have a convalidation by radical sanation of the civil marriage between a Catholic who wants to be in a valid marriage and a non-Catholic who thinks the marriage is already valid and won’t consent to a new exchange of consent? Oy, I’m getting a headache.

That’s why you’re the canon lawyer and I’m not.
I suppose I should have been more technical, particular and specific and said that I was only talking about “simple convalidation.” Anyway, common parlance, pretty much across the board, is to refer to all of them as “convalidations” no matter what. At least that’s better than “getting my marriage blessed.”
I guess I might as well get into this a bit more. Part of the reason for the misuse of “convalidation” in this circumstance may be the fact that there wasn’t really any “official” commentary on what happens when a Catholic enters a civil union and then wants to marry in the Church–is that a simple convalidation according to the terms of c. 1160? It would seem so, since canon 1160 is in the section of the Code dealing with “simple convalidation.” That canon states:
A marriage which is null because of defect of form must be contracted anew in canonical form in order to become valid…
The key word there is “defect.” At times, that word is understood to be equivalent to “absence” as in canon 1095.2 which addresses a “grave defect in discretion of judgment.” That “defect” is, in actuality, an absence of discretion. At other times, it is understood to mean that something is there but it is not complete. A “defect” of marital consent can be an intention against children; but other than that, the person has proper, marital consent. Marital consent was not “absent.”
As far as “canonical form” is concerned, we always distinguish between a defect and an absence. If two Catholics exchange consent before two witnesses and a Catholic priest who does *not *have the faculty to assist at a marriage, that is a “defect” of form. If they go to the courthouse, that is an “absence” of form. Is canon 1160 meant to address both scenarios?
For a while, even among some high-level canon lawyers, the answer was “yes.” In 2005, the Apostolic Signatura issued a clarifying statement and a subsequent decision of the Rota made it clear that c. 1160 should be understood to refer to a “defect”, strictly speaking. A total lack of canonical form is remedied by a marriage in the Church and not a “simple convalidation.”
Regarding sanation–yes, that throws another wrinkle into the situation. A “civil union” is a non-existent marriage in canon law not because of a problem with the actual consent of the Parties but because of a problem with how they expressed it. The Church can decide how that “ineffective” expression of consent can be recognized. The legal system of the Church is independent from the civil law. Both systems, though, can chose when to accept “facts” from the other system. Adoption, for instance, is an entirely civil process/fact which the Church choses to accept and make her own.
As for “civil unions”, then, there is no question that it is legally possible for the Church to allow that “juridically ineffective” expression of consent be recognized/validated by an act of the proper authority in the Church. It is also pastorally useful since, as you note, it is common for the non-Catholic Party to think that there is no point in another wedding. The non-Catholic actually has some justification in that: again, the Church thinks that the consent of the Parties was, in itself, proper. If the consent they expressed was not appropriate/actual, there could be no sanation (cf. c. 1162.1).
In practice, this use of terminology makes no difference to the people involved. They’ll “get married” according to canonical form no matter what term is used (“church marriage”, “convalidation”, “blessing”). As a matter of fact, though, proper terminology leads to proper understanding and that leads to proper practice. Personally, I’d be happy if we never used “blessing” again. I can at least palate the (improper) use of “convalidation.”
Dan