On my desk lie several ORDOs; I have just looked at the admirable S Laurence Press ORDO and the less admirable SSPX product*. On Sunday after Christmas ... back in those happy days before the Holy Family had migrated from Epiphany I to Christmas I ... SLP, reflecting the pre-Pius XII usage, gives S Stephen. SSPX, following the Bugnini dislike of Saints on Sundays, gives the Sunday (which SLP transfers to the free feria of Thursday; I wonder what the antiquity of this usage is and what readers think of it). SSPX does at least, unlike post-conciliar calendars, allow S Stephen a commemoration. Common Worship continues an Anglican tradition of allowing Saints to supersede Sundays except on Sundays in Advent, Easter and Lent ... or to be superseded and transferred ad lib to a free weekday. In fact, the earlier Anglican custom, dating from the 1928 Prayer Book Calendar (when full provision first began to be made for occurences and concurrences) and in use de facto until the reforms of 1967-1980, followed the pre-Bugnini Roman practice of favouring the Saint. There has been thus a consistent bias in the Anglican Patrimony of being more relaxed about Saints on Sundays than Roman tinkerers are.
Bishop Andrew Burnham's book commends this Anglican instinct. It has practical and didactic advantages: under the modern Roman system, Sunday worshippers never get exposed to all those Saints' days. Theologically, it might be pointed out that each time martyr sheds his blood in witness, this is an entering into, and expression of, the Pascha of the Lord's Suffering and of his Entrance into Glory; and is thus by no means unsuitable to be commemorated on a Sunday.
*I would be very happy to have look at the American SSPX ORDO, which is at least in Latin rather than in some degenerate Gallic Romance dialect. But Angelus press tell me that the packaging would make it prohibitively expensive for them to send me a review copy.