I know for me, as a person with ADHD, I have MUCH better self control when I'm on keto then when I'm not. It's the main reason I stick to the diet.
I would not relate this point to serum glucose in any way, however.
However, I seriously doubt this is specific to self control. I would imagine performing any action that depletes glucose in the brain would have the same effects. Prioritizing tasks and deciding tasks to delegate are a couple I've read which are supposed to be very energy-hungry (I've been reading 'Your Brain At Work' recently and its mentioned in there).
Garbage in, garbage out as the saying goes. Proper diet will improve brain function and "self control".
From the paper:
"Resisting the temptation to eat the cookies presum- ably depleted an energy resource that could otherwise have been used to persist on the subsequent task"
To your point, the best way to diet then would be to avoid the temptation which would mean less use of glucose in the resisting of it.