I still think this is too limited. Analogous to how Keynes said classical / Ricardian economics discussed distribution of goods given a fixed level of production, the linked article doesn't consider that the maximum productive output on any given day is not the same, even when the 3 variables considered are maximized.

"Behavior" here seems to be a boolean, "why we take action or not take action at any given moment", but I think many people who ask how to be more motivated or productive are asking about total output, not just about the ability to begin a task. They might be able to sit down at their desk and start working, for example, but not be able to continue long even after doing all the tricks.

In my experience, there is some sort of "mental energy reserve", and as that is exhausted it becomes increasingly difficult or maybe impossible to do any further productive work. If you are doing a strength training workout in the gym, no amount of "motivation" is going to let you continue lifting heavy weight indefinitely. I haven't seen much research to quantify that "mental energy reserve" or quantitatively measure how different tasks exhaust it.

There also seems to be some task-related inertia.