The Father Lasance New Roman Missal 1957 edition, has a wonderful chart on page 72 indicating the postures at ALL Masses. (If anyone has a copy and could post it, it would be worth while copying and printing for reference. Sorry I don't know how)
At EVERY Mass, Low, High, Requiem, Solemn, and Solemn Requiem, we are to KNEEL from the Sanctus till Communion.
The SSPX has been trying to get us to stand for years, putting out new postures for Mass that are similar to the Novus Ordo.
Kneeling in reverence at this time makes sense.