Yup so once you get that chassis you can then order anything you want and to change out how the gun is configured.
Ie, say you bought a compact p320, but you decided you want a full size. All you need to do is pick up a new full size slide and barrel then order a full size grip (about $40) transfer the chassis over to the new grip (about 5min tops) toss on the new slide and good to go. Same with if you wanted a subcompact.
It' the main reason (along with cost) they beat out that shit entry glock tried to pass off as "modular"