Which they have done away with. The website now tells passengers to contact their "partner" Uber directly. Premium passengers are given a pretty measly $10 credit towards an Uber ride, and that's per reservation, not per person. It looks like the entire last-mile Brightline+ offering has pretty much been dismantled, except for pay-per-ride airport shuttles and shuttles to sports events & concerts. There's no mention of the former Aventura mall shuttle.
But Brightline does not permit platform access except through their station house, so the proximity of the far end of the platforms doesn't help.