New facts learned earlier in Day 4 about Day 3

At lunch I was reading the Preface to the Vatican Edition of the Roman Chant and on page xvj at paragraph VII it says in part,

When the Preface is finished, the choir goes on with the Sanctus and Benedictus. If these are sung to Gregorian chant they must be given without a break; if not, Benedictus may follow the Consecration...

That is what happened yesterday. A polyphonic Sanctus preceded and a polyphonic Benedictus followed the Consecration, confusing me no end... well, end, I guess.