Set on "One Shot" you focus and recompose (perhaps the focus sensor isn't close enough to the edge of the frame...) and squeeze off a short burst on motor drive setting.
Will the camera re-focus on the new "target" of the chosen focus sensor after the first capture?
What if the focus setting is AI Focus or Servo? I think here it WILL refocus.
I called Canon this evening to ask, and the gentleman in Chesapeake, VA, said, "Hmmmmm...." and that he will get back to me.
...sometimes I shoot manual focus again. I get frustrated by constant moves back to the focus point, make another half-press... well, you get it: if the light, subject, and available depth-of-field allow manual focus -- and will not change -- I am starting to go back to the "old" way. Canon suggested I try using the AF-Focus button and that's interesting work-around, but I would try to assign the "M-Fn" button to that task, because it's near the shutter and it uses the index finger. Faster reaction than jamming my thumb up by my cheekbone to find that AF-Focus button among the three that are there.