A few points there.

1. I have edited the previous message to add something.

2. I too wonder if the painting is misleading in showing the surcoat.

3. I do not see how the Queen's white linen gown "bared her chest" any more than the Hartnell dress did. I have always assumed the Queen was anointed on her bare flesh already visible at all times.

4. It seems to me that the canopy was a modesty measure when a king was bared to the waist, and the canopy has continued to be used as a tradition.

5. Which raises the question of whether a Queen Regnant was ever stripped to the waist in the past for the Anointing.