I finally received a payment!
I phoned the US office a week ago and talked to a very nice and tenacious woman who said that she saw no reason my claim wasn’t approved and promised to track it down internally. The following day the website said it had been approved and the back payment dropped into my account this morning.
So, short timeline is initial request December 2023, interview in February, approval and back payment in August.
I hope you all get a quicker response when it’s your turn.