People stand because it's a liturgical tradition to stand for the singing of the Alleluia which precedes the reading of the Gospel.
If the King George II story is true, then he stood because of that tradition. Not even the most ardent royalist would follow a custom simply because some previous monarch did it once. ("The queen once opened a closet door with her left hand, and so, we all now use our left hand to open closet doors!")
One stands for the Hallelujah, not for some dead potentate whose foot fell asleep that one time.
If the King George II story is true, then he stood because of that tradition. Not even the most ardent royalist would follow a custom simply because some previous monarch did it once. ("The queen once opened a closet door with her left hand, and so, we all now use our left hand to open closet doors!")
One stands for the Hallelujah, not for some dead potentate whose foot fell asleep that one time.