Of course the position "only add something to your todo list if you are going to do it immediately" is ridiculous at face value.
But if you are a bit more generous with its intentions, then there is something that really chimes with me about it.
I work in engineering support to oil and gas operations (but I'm sure this is applicable to many industries), and we have quarterly workplans and pretty fixed budgets. Of course our budget-holder typically asks us to do more work than we are able to deliver, so I will often have to say "this job does not make the priority list for next quarter, but we can do it the quarter after next?".
However, I've found a pretty good rule of thumb is that if a job was not high priority enough to win a place on the next quarter's to-do list then by the time the following quarter comes around, it will probably get bumped off the priority list by something else higher priority. In other words, our limited budget means there is always some 'cut-off point' where work that looks important is still not quite high enough priority (compared to our other work) to ever get done.
It is easy to 'form a long queue' by saying yes to work and letting it sit on our to-do list forever, but just slightly too low down to ever get done. But in our industry at least, there's a small overhead involved in just keeping that work around and passing the ownership of the task from person to person.
A more realistic rephrasing could be "if you're adding something to your todo list and it's not high enough priority to bump anything else, consider how much inefficiency it will cause long-term by it just sitting in your queue for months"
Maybe a little silly for your personal todo lists, but I think the idea has some applicability at a larger scale.