I think that's not too hard to surmise, Bishop. The norm for the time when the practice began was probably once a month communion (or less). So most Sundays, the missal stand stood in the middle bearing the Altar Book. I'd be willing to wager that what was usual (for the p. 5 or 32 Sundays) became thought of as simply the norm even for a p. 15 Sunday. I remember for some time after we had gone to the weekly Eucharist, the elders persisted in moving the missal stand to the center of the Altar after the Divine Service as they assisted with cleaning up afterwards.
Interesting -
a) they went back to the old habit
b) they were elders, not the altar guild. My deacons and elders can and do "clean up," but the altar guild and acolytes are the major movers and cleaners.
c) we had the double benediction deal at my home congregation in Milwaukee - p. 5 benediction followed by shortish p. 15 and subsequent second benediction for those who stayed. I'm trying to remember if the missal was in the middle and the elements on the edge, but that could have been the case. Except that our pastors chanted Matins and the p. 5/15, so were "high" church for those parts at that time.
Dave Benke