As E! News points out, Harrison apparently contributed voiceover work to the finale of the show's 25th season, with his voice appearing several times throughout the episode.
At one point, Harrison even promoted the After the Final Rose host replacement, Emmanuel Acho — despite the fact that Acho's participation was announced after Harrison took his leave of absence.
So, to recap, it seems like Harrison might've kept working on the finale after claiming he was stepping away from the franchise for now. Weird!
The Bachelor Diversity Campaign — a campaign run by a group of Bachelor fans whose stated aims are "anti-racism in the Bachelor franchise" — noticed Harrison's inclusion in the finale and pointed it out on Twitter.