With the Renegade the upper is the receiver and the lower is just "bottom metal" so legally each Renegade upper is a separate firearm but at least it's NR. Probably no benefit from buying an upper-only unless you have an expensive trigger group you want to share between rifles.
Totally different dynamic from an AR where there was so much legal restricted hoopla around a lower receiver that it made sense to build an extra upper and swap around.