Where do you suppose the answer to that question is going to come from? Something posted on a message board or by asking immigration? I don't know what makes most sense to anyone else, but I know what makes most sense to me.
What makes most sense to me is after getting the retirement visa, 90 days later just go to immigration and show them the updated bank passbook. If they're not interested, let them be the ones to tell you.
Maybe I'm missing something. I don't understand why this is even an issue. Just show them the bank passbook. Takes all of 30 seconds. What's the problem?