22.3 is a negotiated, protected floor number of employees and if they hire any more then they could be subject to layoff. You then revert to PT equal-seniority contract and pay while bumping one or two PT employees off of their respective shifts and then these PT employees in turn would be laid off (or more likely stop hiring and send people away in their 70-day packet).
My center has made quite a few 22.3 movements lately not sure about the details but it definitely seems like they are creating more than the minimum # of positions. Probably will save them money to use 22.3 instead of PT in many parts of the building regardless.