Silly question: why not? Has this terminology been officially forbidden? No. Has it even been officially criticised? No. Has there been some official push for terminological uniformity? No.
Silly questions get asked, however, and I've replied to a particularly silly example which appeared in the Catholic Herald letters pages a couple of weeks ago: here's my letter in reply.
Fr Leo Chamberlain (Letters, April 1st) takes exception, not for the first time, to the phrase 'the Traditional Mass'. It should be noted that the Motu Proprio is concerned with legal realities, not verbal issues, and nowhere forbids this phrase. Indeed, Cardinal Catrillón Hoyos, as President of the Pontifical Commission Ecclesia Dei which was given the right to 'exercise the authority of the Holy See' in the application of the Motu Proprio (section 12) immediately introduced a new description, 'the Gregorian Mass', referring to Pope Gregory the Great, whose codification of the Missal was a key moment in the tradition of which the 1962 Missal is the fruit.
If Fr Chamberlain objects to the term 'Traditional Mass' presumably he will object equally to the term 'Gregorian Mass'. Is the 1970 Missal not just as much a fruit of the Gregorian tradition?
It seems not. Normally, each missal published by the Holy See replaces and abrogates the one preceding it. Many argued the 1962 Missal was abrogated in this way. The only alternative is to say that the 1970 Missal is so radically reformed that it establishes something distinct, leaving the 'previous liturgical tradition' (as the Motu Proprio calls it) intact. In other words, there has been a discontinuity in the Church's liturgical tradition.
This argument has been finally and definitively vindicated by the Motu Proprio, and like or not Fr Chamberlain must live with it.
Chairman, The Latin Mass Society
There are many practical reasons for retaining the term 'Traditional Mass' - among other descriptions.
1) It is widely understood.
2) It is not specific to the year 1962. It evidently applies to the 'old' Missal as changed in 2008 (the new Prayer for the Jews), and practices pre-dating 1962 (which are inevitably a staple of pub discussions among trads). It refers to the Mass as developing organically from the time of Pope Gelasius to the present day.
3) 'Traditional' can be applied equally to the Breviary, the other sacraments, and the pre-reform versions of other rites and usages. The Dominican Rite hasn't been made the 'extraordinary form' of anything; the Mozarabic Rite, the Ambrosian Rite and the Carthusian each have two forms, reformed and unreformed, and these aren't officially described as different 'usages'. Are we to talk about 'extraordinary form' Vespers? That would make no legal sense.
4) It also applies naturally to theology and spirituality, and to devotions, which naturally go with the Traditional Mass. Extraordinary form Stations of the Cross, anyone? Usus antiquior theology of the atonement?
5) 'Traditional liturgy' goes logically with the terms 'Traditional Catholics', 'Traditionalist' and so on. These terms describe real phenomena in the Church which we have to talk about from time to time in a clear and descriptive way - whether we like what we are talking about or not.
Finally, and perhaps this is because I am an academic trained in analytic philosophy, it drives me nuts to hear endless disputes about words. The important thing is that people know what the words mean. If we can have a discussion without ambiguity and equivocation, it matters not a jot what words are used. In theology some concepts can only clearly be expressed by words which have been more or less invented (or redefined) for the purpose (transubstantiation, consubstantial, incarnation), but that is not at issue here. Merely verbal disputes are childish.