Is that discount only for active duty I assume? Did you order direct from CZUSA?
Can't say for absolute certain with the new models, but in the past some stocks would fit others, depended on the barrel contour and bottom metal.
I wish I could remember more specifics now, 4-5 years ago I went through that. My 527 Grendel is based on a 527 Carbine in 7.62x39. But it's wearing a stock from a 527 Varmint Kevlar in .223. The bottom metal fit fine in that case, but I think some models it may be different. Obviously the wood stock from the Carbine didn't fit the Varmint Kevlar barreled action, the barrel channel wasn't deep enough and it would have looked odd anyway. I ended up selling the stock. Surprisingly I had an easier time selling the 7.62x39 take-off barrel than I did that stock.