But the law also indicated that if a priest creates a situation in which a group of reasonable people (a hypothetical, not actual group) would fall into error, then there is Common Error of Law and jursdiction is also supplied, even if there is no "honest error" at all.
No, I had already addressed this above. There is no common error of law when the (actual or hypothetical) community actually knows the truth of law. Yet, according to the opinions of the moral theologians that I have already cited, when the (actual or hypothetical) community is in common error regarding the law -- "one or the other" who actually knows the truth -- can benefit by a valid confession. In other words, supplied jurisdiction presupposes real common error (regarding factual matters or the law) among the (hypothetical or actual) community.
You are confusing the two concepts, NSM.
Common Error of Fact is a factual error. If people know that a priest does not have jurisdiction there cannot be Common Error of Fact, since there is no factual error.
Since the law itself lists Common Error of Law as an entirely separate kind of Common Error, then it is clearly different. This, it seems you fail to understand.
Common Error in Law is not "error regarding the law". It is a legally created "Common Error" which is not an actual error. It is not a error regarding the application of law. It is a legal fiction, of which there are countless other examples.
Because it is a legal fiction, the standard which must be met is a situation or fact exists, and this situation or fact would cause a group of reasonable (average) Catholics to believe that a priest has jurisdiction. It is not necessary for an actual group of people to be in error, only that a group of reasonable people would be in error if they were presented with the general situation.
There is no consideration of what they know or don't know, or what they should know, or whether the group is an SSPX group and whether the priest has informed them that he has no ordinary jurisdiction. None of this matters. If we insist upon narrowing the group or putting caveats on this hypothetical group of "average Catholics" we make Common Error of Law into Common Error of Fact. They are not the same, but two very different concepts.
The situation is analyzed as follows: A man dressed as a priest enters a confessional and shows himself ready to hear confessions. The average Catholic would believe that he has the faculties (if they even know he needs faculties), so a group of average Catholics would also believe this. Thus if a man dressed as a priest enters a confessional and he lacks jurisdiction then it is supplied, provided he is a priest.
I have presented at least two post-1983 Canonical authorities who use this exact situation as an example. The New Commentary on Canon Law published in 2000 even uses this example, and they do no make any kind of distinction regarding a situation like the SSPX, even though if your claim is correct, that example would provide a perfect example of the limitations of this law.
The fundamental problem that I think you are making here, NSM, is not making the distinction between what is truly meant by Common Error of Law and the distinction between the two.
Beyond this, there is also doubt which we have not discussed. Doubt is defined as a situation where there are reasonable arguments for and against a proposition. Clearly if we're able to make reasonable arguments here (I'm not trying to prove that SSPX confessions are valid, only suggest arguments as to why they may be), then we also have a situaion where there is doubt, and in case of doubt, jurisdiction is supplied.
If you do have Canonical authorities (particular post-1983) which demonstrate that Common Error of Law only applied in ignorance, then I would appreciate those citations.