You should always use two nuetral's and here is why.
One of John Deere biggest class action lawsuits involved the John Deere 350 bulldozer series made between 1965 and 1988. The 350 model, 350B and some 350C models did not have a slot in their standard transmission shift pattern to even put the bulldozer in neutral. These tractors have a hydraulic reverser so it can be shuttled between forward and reverse on the fly without stopping; something a bulldozer does all day, every day. But this reverser has a neutral slot.
The problem was, the lever was where the operator gets off and numerous people lost their lives when they hit the reverser lever on their way off the operators seat. This was especially true after the reverser linkage got worn over the years. I never was killed obviously, but I cannot count how many times I stepped onto the track, bumped the reverser lever and nearly got trampled. Now I have got into the habit of shifting BOTH levers in neutral before stepping off the tractor. In logging operations, this happens a lot...on and off, on and off...rinse and repeat...but it is the safe habit to get into.
With John Deere, the class action lawsuit was started because people physically could not shift the main transmission into neutral. By the time my John Deere 350D was made (my 1988 tractor), the tractor had the oversight corrected.
History lesson of the John Deere 350 be worthwhile or not, you would indeed be safer IF you got into a 2 neutral habit without question in my opinion. The worst case scenario with 2 neutrals is, you jump on and go to take off and realize you are in neutral on one lever. The worst case scenario with only one neutral is, you inadvertently shift the tractor into gear and run over yourself on the way out.
I once knew a man in Maine who was killed when he was shoveling sawdust into the bucket of a big loader. The bucket was full so the operator went to haul the sawdust off for dumping, and was in forward when he thought he was in reverse. When he went to hit the gas, he cut the man in half killing him. Would (2) neutrals have helped? I am not sure, but a second step might have made him think twice?
BUT...I admit I am probably the worst operator on this forum as I have got so complacent on certain things. I hope others really get into some safe habits right off the bat. That is not judging others, that is hoping others are more safe than me.