Here’s the one advertised as Pineapple Passionfruit where the ingredients don’t list actual passionfruit. It has “natural flavors”. Maybe that includes extract from passionfruit, maybe it’s entirely from other fruits, but they’re not required to say.
The FDA makes a distinction between “natural” and “artificial” flavor based on source, but my point is that distinction itself is sometimes completely pointless and misleading. For some flavors there is truly zero difference. I suspect that’s the case for passionfruit, so it’s possible customers are worked up over nothing.
(I would highlight pineapple but Starbucks actually claims there is real freeze-dried pineapple chunks in their drinks, and that seems easy to verify)