This is one of the reasons I prefer the EF breviary to the OF. If there’s a feast day that coincides with Sunday, it’s commemorated with the office of that day (if the feast day of St. Francis de Sales was Sunday instead of today, the Sunday office would be said, along with the collect and antiphon for the Gospel canticles and the response to the reading).
This thread appears to be about liturgical
concurrence which is when Vespers (Evening Prayer) of the current liturgical day coincides with I Vespers (Evening Prayer 1) of the
next day. What you’re talking about is liturgical
occurrence which is when two or more Offices/Masses occur on one and the same day.
Also, the example you gave isn’t correct even for liturgical occurrence on the 1960 calendar. The 1960 rubrics state that 1st Class Sundays permit only a single
privileged commemoration and 2nd Class Sundays permit only a single commemoration of equal rank (i.e. a 2nd Class Feast). Privileged commemorations are 1st Class Feasts, Sundays, days within Octaves, Ember Days, the ferias of Advent, ferias of Lent, ferias of Passiontide, and the Greater Litanies at Mass but not in the Office. St. Francis de Sales is neither 2nd Class nor privileged and so would never be commemorated on a Sunday.
As an FYI in case you’re wondering, the rules for concurrence are as follows: If the two Offices are of different rank then the Vespers of the higher ranked feast is said and the other is commemorated
following the aforementioned rubrics. If the two Offices are of the same rank then you say Vespers of the current day and commemorate I Vespers of the next day, again, following the aforementioned rubrics.
In other words, you would only commemorate the II Vespers of Saturday if it is a privileged commemoration
and the following day is a 1st Class Sunday. If the following day is a 2nd Class Sunday then either you would not commemorate Saturday’s II Vespers (in the case of a 3rd Class or lower Saturday) or you wouldn’t even say Sunday I Vespers, instead commemorating it (in the case of a 1st or 2nd Class Saturday) If St. Francis de Sales fell on a Saturday you would completely omit its Vespers no matter what because it is neither 2nd Class (in case of a 2nd Class Sunday the following day) nor is it privileged (in case of a 1st Class Sunday the following day).
Clear as mud, no?
