My '52 Liber Usualis calls for the Preface of Christmas to be used at Votive Masses of the Blessed Sacrament (p. 1283). I confirmed this with the '61 version, which I assume adheres to the 1960 rubrics. Both reference the preface section on p. 8, which prescribes this preface to Corpus Christi, justifying its use for this particular votive Mass.

Yet #484 of the 1960 General Rubrics, which deals directly with the Preface of Christmas, does not include the aforementioned Mass in its list (cf. https://www.divinumofficium.com/www/horas/Help/Rubrics/Missal1960 rubrics.html#6). Additionally, Divinum Officium prescribes the Common Preface for the Feast of Corpus Christi under the 1960 rubrics, but the Christmas preface for the 1955 rubrics.

I'm thinking this was a change made between the '55 and '60 calendar that Solesmes either neglected to update or simply put into practice in the monastic realm. Does anyone have any insight into this minor oddity?