Ah I see, the task currently being done is not part of the stack.

I can see this working with tasks of similar length and difficulty. But what about when one task is significantly shorter than another and partly time dependent? E.g. in this case, while your essay is more important, it might take several hours to do well, during which the dishes will moulder and annoy your flatmate. Whereas the essay will not e altered during that length of time. I acknowledge that this is a possible way to rationalise procrastination, but there would be cases where it was true.