Fr. Jungmann was a good historian and nowhere would he have suggested that the Missal of St. Pius V was a "new rite".
This new rite alone is to be used unless approval of the practice of saying Mass differently was given at the very time of the institution and confirmation of the church by Apostolic See at least 200 years ago
I know it's hard to believe, but Pius V did not write his bull in English. :)
Ut autem a sacrosancta Romana Ecclesia, ceterarum ecclesiarum matre et magistra, tradita ubique amplectantur omnes et observent, ne in posterum perpetuis futuris temporibus in omnibus Christiani orbis Provinciarum Patriarchalibus, Cathedralibus, Collegiatis et Parochialibus, saecularibus, et quorumvis Ordinum, monasteriorum, tam virorum, quam mulierum, etiam militiarum regularibus, ac sine cura Ecclesiis vel Capellis, in quibus Missa conventualis alta voce cum Choro, aut demissa, celebrari juxta Romanae Ecclesiae ritum consuevit vel debet alias quam juxta Missalis a nobis editi formulam decantetur, aut recitetur, etiamsi eaedem Ecclesiae quovis modo exenptae, Apostolicae Sedis indulto, consuetudine, privilegio, etiam juramento, confirmatione Apostolica, vel aliis quibusvis facultatibus munitae sint; nisi ab ipsa prima institutione a Sede Apostolica adprobata, vel consuetudine, quae, vel ipsa institutio super ducentos annos Missarum celebrandarum in eisdem Ecclesiis assidue observata sit: a quibus, ut praefatam celebrandi constitutionem vel consuetudinem nequaquam auferimus; sic si Missale hoc, quod nunc in lucem edi curavimus, iisdem magis placeret, de Episcopi, vel Praelati. Capitulique universi consensu, ut quibusvis non obstantibus, juxta illud Missas celebrare possint, permittimus; ex aliis vero omnibus Ecclesiis praefatis eorumdem Missalium usum tollendo, illaque penitus et omnio rejiciendo, ac huic Missali nostro nuper editio, nihil unquam addendum, detrahendum, aut immutandum esse decernendo, sub indignationis nostrae poena, hac nostra perpetuo valitura constitutione statuimus et ordinamus.
As you can see, in the authentic text he doesn't mention anything about a "new rite".
* Try reading "The Mass of the Roman Rite." In Vol one, pages 127 - 141 when he describes the new rite and how the Commission charged with creating it, among many other things, "The members of the Commission were not held back from doing away with added trimings which the pious mind considered untouchable, like the already traditional Marian insertions in the Gloria in excelsis. Finally, it was because of the humanistic artistic spirit that the Council did nothing...
In a few words Jungamn dissapates the fog of lies about the "immemorial Mass which never tossed out any tradition..blah, blah, blah
One who reads real Liturgical histories written by trained and renowned Ecclesiastical and Liturgical experts, like Jungmann, is immune from being influenced by the error-laden polemics of those written by lay converts - such as the ones by Davies - which have seduced many lost souls into abandoning Holy Mother Church for the schism.