When one normally uses the brakes, the purpose is to stop forward or backward motion. The foot control normally goes to neutral. I don't see a situation where you would use the brake and the foot control on the Kubota at the same time, however on the PT, if you take your foot off the treadle, you might go to neutral. Most cases you have creep in fwd of rev. On just about any hydra-stat, if backing down a ramp, you have to think in reverse logic, press the fwd treadle to slow speed of the machine going back wards.
Years ago I had a serious accident with a Dixie Chopper hydro stat. I had cut this hill, 40 ft wide and 300 ft long which had 4 foot drop at the bottom edge to the next level. Early morning, wet grass, I made a slow turn down hill, and started sliding down, building up speed. I had the hand controls in full reverse, but nothing happen. Right at the edge, I put the hand controls in neutral and dove forward as much as I could. The Dixie Chopper landed on my legs and pinned me under the 500 lb machine. I lay there with the pain and hollered for help. Nobody came, so I managed to drag my legs from under the Chopper, and finally got some help. I missed an Air Condition unit only by inches. After all the x-rays were done, the only serious thing was that my thigh muscle was split. I am glad that it didn't land on my head, and the way it tumbled off the ledge, it would have drove my head into the ground . It did not have ROPS.
Lessons learned, never cut a hill that has wet grass. and always turn uphill. Going is reverse and applying brakes isn't going to help on wet grass.
A seat belt, if used in this situation , you would be talking to a ghost.
Another useful little hint. if cutting around ponds or lakes, even if you have ROPS, don't wear a seat belt, unless you want to. Why, as you start to roll, you will be thinking to grab something to hold on to, and ignoring that seat belt and when the tractor or whatever machine pulls you under water, you might make it, maybe not . In the Navy, they taught us to get out of an upside down situation under water, wearing full glight gear, helmet, boots, and wearing a seatbelt and shoulder harness. Let the machine stop, unbuckle ,watch the bubbles and follow them to the surface.