I just called Amex to see if they would double my points. I use an Explorer and Edge cards linked to Ascent.
They noted they have not seen a large balance like mine for some time and would like to encourage someone with my spending habits to maintain loyalty to Amex. However, the staff making such decisions (? senior marketing team) are on leave and no promises were made. They will "try to do something" and will be contacting me after 7th January....
If they do not double my points balance, then we will need to assume that decisions about this are not directly linked to spending habits alone.