The feeling of the boat being sent away at the finish to acelerate without any loss of speed. May be a result of ismached power application on the drive. Not just at the finish, but during the drive. The oar will go deep then wash out in a rainbow motion. Starting with the legs is a linear motion that keeps the oar shallow.
Some people feather while they are still in the water at the finish.
That s bad. Need to let the blade leave the water then feather. Too big down and away push at the finish. Oar height will be really high at the finish. Of course, there are some limitations to the awesome power of the cox and things that are just too subtle to see.