Depending on hull shape, an offside lean may work better than onside. I know that in my Rapidfire, if I lean away from the paddling side, then far less correction (almost none) is needed than if the canoe is sit centered or leaned onside. I have found the same true in other canoes as well. Clearly those racers in the video are not heeling offside
Hull width makes a big difference in whether one can comfortably and effectively heel to the on-side or off-side. In a narrow solo canoe, it's fairly easy to heel either way. In a wide tandem canoe, such as those being paddled in the old video that Benson posted, it's much easier, more comfortable and more natural to shift your body weight and hence your heel to the on-side. I also think most of those paddlers were correcting a bit at the end of each stroke, but with a very quick slice out that is sort of a mini-Canadian stroke correction.