I have a Toro 924 Power Shift that has been a great machine.
My reverse system operates just as you have described. The shift lever is held in reverse by the drive clutch control. I believe it was designed this easy to allow you to turn slightly while you back up. This would be very difficult to do if you had to keep two hands on the machine.
I don't recall the chute vibrating out of position but I am usually changing it so often that I may not notice.
