Isn't that literally the point? If you can do your task in 10% less time, and then end up spending that 10% procrastinating on HN, then you still win - the task gets done, and you also get to sneak in something nice. And if you find you'd rather spend that time on something else, or doing more work to finish everything faster, you can choose to do so. Optimizing work gives you choice what to do with the time saved; the default may be that you waste it, but now you have options.