They definitely make their own wings (per their
Production page) but it's less clear about the backplates. I've seen elsewhere on SB the claim about ScubaPro and Halcyon using the same manufacturer for plates, but no source for it. Based on H's production page regarding how they review/revise materials selection, it's not impossible they may have switched up manufacturers, or use multiple due to the various materials they employ in their plates.
Consider also how easy it is to replace parts in the ScubaPro, especially if you're looking at the Pro vs. the Pure. One benefit of BPWs lies in the ability to service the gear with parts more commonly accessible than what you get in other BC designs.