Rad Trad Canon Fabrication

I have noticed there is widespread dishonesty, incompetence and fabrication in the groups of people that style themselves "traditionalists," whether they be SSPX, SSPV and especially the Sedevacantists. Here is one example

If any ecclesiastic or layman shall go into the synagogue of the Jews or to the meeting-houses of the heretics to join in prayer with them, let them be deposed and deprived of communion If any Bishops or Priest or Deacon shall join in prayer with heretics, let him be suspended from Communion" - III Council of Constantinople (sometimes cited as II Council of Constantinople)

This canon I have not found in any of the four Councils of Constantinople. Nor in Denzinger! This "canon" is quoted by this list of incompetent sources (exclude me since I will appear on there for this article). This has a number of Sedevacantists and "rad trads" site and forums.  Notice none of these sites even bother to quote the "canon number" or section of the council! And as I mentioned above--they are inconsistent with what council it is! I accidently ran into what I think is the REAL source of this canon--the "Apostolic Constitution" which was written around AD 400--this document lacks ANY authority and cannot be quoted as part of the magisterium! Here is what the "Apostolic Constitution" says:

If any one, either of the clergy or laity, enters into a synagogue of the Jews or heretics to pray, let him be deprived and suspended. --Apostolic Constitution, Books VIII, Canon 65

 The Rad Trads have used this against Popes John Paul II, Benedict XVI, and Francis (I) to try to condemn them for entering synagogues--which they did! But the issue is did the popes pray "with" the Jews, or AT their place of worship? Its more likely the SECOND case! Either way, NO ONE is bound by the Apostolic Constitution! In any case, this shows that ignorance, incompetence, plagiarism, and dishonesty are PREVALENT among the "rad trads."