As for standing, I think the excuse for it is that they want the congregation to join with the choir. Therefore, we stand to sing the Kyrie, the Sanctus, the Agnus Dei.
As for me, I consider being in the choir a job, a sacrifice, because I can't pray the mass. That is why I would not be in a choir, unless, the chapel I attended had two masses, in which case I would sing in the choir during one mass, and attend the other mass and pray without singing.
Anyhow, I agree that changing the 1962 postures to the 1965 postures is the objective, and that the "to sing standing with the choir" , is just an excuse to accomplish the objective.
I too think we are being "slow boiled" towards a "reverent" Novus Ordo.
"Those who cannot remember the past are condemned to repeat it."