I think most of the commentators have missed the point of the letter.
This letter confirms that Metropolitan Jonah was properly removed from his throne. This ends any argument regarding his restoration.
Moscow is not sanctioning any type of 'lawyering up,' but rather urging a settlement that does not involve a willful humiliation of a former First Hierarch. Were that to happen, the Orthodox world would go into panic mode (let's think, how many First Hierarchs are facing mounting criticism?). One only need look at the Bulgarian situation to understand how hesitant Synods are in removing even the most profoundly incapacitated senior bishops.
Moscow is also not, by this letter, telling the OCA to give him millions of dollars. The typical fate of a retired bishop is a nice apartment in a monastery. No travel expenses, family & friends plan, etc. Metropolitan Jonah never stopped being a monk, and a monk dies to the world. His natural place would be at St. Tikhon's Monastery, the senior monastery of the OCA, along side his predecessor, Metropolitan Herman.