Timesizing designs the length of the workweek as a reinvestment threshold and says to companies, "You can overwork people as much as you want - as long as you reinvest your whole overtime advantage in on-the-job training and hiring" and it says to individuals, "You too can overwork all you want - as long as over this threshold, you become part of the job creation solution instead of worsening the work concentration problem - which hurts you by the way, since you're growing the labor glut and depressing your own pay - especially if you're getting no overtime pay."
Timesizing makes the problem (overtime and overwork) trigger, size, pace, and fund its own solution (training and hiring). And the week-to-week amount of overtime is not rigid and arbitrary because the workweek is no longer rigid and arbitrary - it is linked to vary inversely with the amount of under-employment.