I saw a picture of the carbine after I posted, and had a similar thought. I don’t own one, but it seems from this: https://everygunpart.com/long-guns-kits/hi-point-995-semi-auto-evguf3-vwhd-00.html that the telescoping bolt ends at the front of the “upper” (which is just a cheesy sheetmetal cover), and the rest is just superfluous plastic. Even if I’m missing something, it seems like it would have made much more sense to start with their pistols and add some sort of chassis. I can’t imagine anyone wanting to forego the advantages of a real stock just to save two Fn inches.

Just guessing here, but these look a lot like their respective carbines. I’d bet the barrel is the shortest that the carbine upper could handle, without having to redesign the upper. Look at the 995, it has about 3″ of barrel sticking forward out of the front of the upper, and on the 995P, the front sight is tucked in as close to the upper as it can get.

I’m with you, I’d much rather have an 8″ or 9″ barrel on the 4595P, but that would have meant redesigning the whole front of the gun, and I’m thinking they didn’t want to go through that effort when they could make a “pistol” just by chopping off the stock and shortening up the barrel as much as they could.