After all, does it make sense for everyone to noisily and distractingly drop to their knees while the priest is saying the awesome entrance into the sacred Canon? Would it not be better for all to remain standing at attention as he says "Sanctus, Sanctus, Sanctus..." then sign themselves in union with him (at Low Mass; at High, people should + themselves as they sing "Bene + dictus...") and kneel when he has finished the prayer? I believe common liturgical sense here wins the day.
The significance of the rubrics of Holy Mass and other liturgical functions can take on different sorts of symbolism for attentive worshipers according to their various proclivities and inclinations. As long as the rubrics are followed, whatever symbolism or significance is relatively valid insofar as it is agreeable with holy doctrine, can edify the individual and would be conducive unto the participation of Holy Mass
digne, attente ac devote.
During the Middle Ages, various authors delighted in writing treatises upon the various interpretations of the symbolisms of Sacred Liturgy (mystical, anagogical, allegorical, &c.), the greatest example being Guillaume Durandus. And such mystics as the great Benedictine Virgin, St. Gertrude the Great, found in the texts of the Mass and Office the occasions for ecstatic revelations and the most beautiful mystical experiences in Medieval German hagiography.
The example of the holy Trisagion that follows the Preface here mentioned affords an opportunity to illustrate this point. The interpretation cited above is good, but I personally find it more edifying and more sensible to kneel at the Sanctus.
As the Priest begins to pronounce the seraphic praise of the thrice-Holy God, I cannot but feel myself weighed down with a sacred dread before the ineffable and awe-inspiring Mystery that is to be accomplished upon the Altar. Feeling the weight of my utter unworthiness and of the iniquities wherewith I have coinquinated my soul in a heightened and clearer sense that is unspeakably unnerving and humbling, I cannot but readily kneel down and bow my head at the Sanctus as the bells announce the beginning the most sacred of prayers in the Roman Rite. I can almost hear the ancient Cherubikon echo within the depths of my soul, knowing how unworthy I am, as the Priest enters the hallowed silence of the Canon, like as Moses ascended into the shady cloud on Mount Sinai. I cannot but beckon the pious terror and wonder that seized the Prophets of old when they foresaw the glories of the Incarnate Word: "O Lord, I have heard the report of Thee, and was afraid; I heard, and mine inmost parts shuddered, my lips quivered at the report" (Hab. ch. iii. 2, 16).
But, this is my personal interpretation and point of view. Just like some follow the older prayerbooks and meditate upon the Passion of Our Lord throughout the ceremonies of Holy Mass, so others (like myself) cannot but follow the texts and rubrics of the Mass exactly as they are being recited (or chanted) and done at the Altar in order to gain as much fruit from Holy Mass as one is capable of doing so and enabled by grace and cooperation therewith.