so what would you call it then? You are descending at a low forward speed or even straight down but at maximum available power with the RRPM gently decaying - you have the descent (which you can't arrest) so you are settling and you have max power - seems straightforward to me.
If I were on a descent at max available power and the RRPM was decaying, I'd say I am clearly too heavy to HOGE and am overpitching.