Part of what makes the S2 & Bolt-on range what they are is the 'neck'. By using a Scarf joint, they can make more necks in a short time from less wood (less waste) and a LOT quicker than it takes to make a 'single' piece neck - with all the waiting in case the wood moves/twists after having a chunk removed.
As the Silver Sky has the same 'S2/Bolt-on' neck - albeit with its own headstock/carve and 'in-house' US made pups, that puts it firmly in the Bolt-on range like the Dusty Waring which I have also seen called 'Core' - and always just assumed that this was used as its easier than saying US made Bolt-on range - especially when those models in particular are the only US made version of those models.
With the Silver Sky in particular, 'Bolt-on' is a given for that style of guitar and could get confusing if trying to refer to the way the neck is attached or the range in which it fits in the PRS line-up. US made version is often simplified to 'Core' - especially now there is an SE on the market.
As PRS themselves classify this as part of the 'Bolt-on' range, and classify the core with 1piece necks, traditional violin carve etc then I will continue to think of this the 'same' way PRS themselves do...