The feature was originally designed as the lead to appease Radio 1 before she signed up for The Voice and the team changed direction. Many figured their audience wouldn't be purchasing Kylie tracks regardless.
It was also designed to launch Brooke into the mainstream as she's signed on Sia's label and she co-wrote that track. Sia and Brooke have had career disagreements recently which is partially being blamed as to why the track wasn't selected as the lead also.
It does make sense to release a very Kylie track as the lead now that she's on The Voice. I still would like to hear the song, the Brooke feature never really scared me like it did everyone else.