It's not about agreeing or disagreeing, it's about spreading misinformation. There is no such messaging from MOE HR at the national or system wide level. Full stop. You are spreading wrong information.

There are a few possibilities why you might have come across an age recommendation, for example your cluster board or HR is responding to an observed trend of underperforming middle managers in a particular school or group of schools, and gives a targeted recommendation to the Principal(s) concerned about their MM development process. And maybe when this message was cascaded down to you, you may have interpreted it as a HR guideline.

It could have been a targeted message to specific schools of concern, but it is definitely not a system-wide message from HR.