This question was asked only a few months ago in PPPRuNe.
This was first implemented some years ago and the number of a/c with this option is increasing. I cannot say which particular a/c have it but it is probably on new and available as a retro fit during an overhaul. (Someone will be along in a minute to tell us!) The lights appear to go "from full on to practically off" as the flash unit applies power again before the filament has fully extinguished.
As you discovered, it draws the eye more rapidly than steady lights. You will find that the lights stop flashing shortly before touch down.