I thought the head of optiboot development was in your arduino repo
It was, but I decided that there needed to be a separate head for optiboot developments that weren't relevant to the Arduino core platforms. Of the ten changes that have been made since the 4.4 version deployed by Arduino, only one is relevant to the "real" arduino cores (and that not until they upgrade compiler versions.) Most have been for the 1284 (which had never been part of an official Arduino board.)