[jrny]

I don't think the priest actually celebrated the Mass of St. Pius V on Sunday. I read that as his mentioning the occurence of the feast.

Of course, in both calendars, the Mass of St. Pius V would not be allowed to be celebrated on a Sunday (Third Class Feast vs. Second Class Sunday), unless in some particular places, St. Pius V is a First Class Feast.

[ELS]

I don't think the priest actually celebrated the Mass of St. Pius V on Sunday.

I don't think so, either. However, he referred to the feast according to the current liturgical calendar. IMHO, it is akin to mixing rites.