Why would it be inaccurate? Why specifically would the bottom two barrels be inaccurate?

Regulated barrels have their hurdles, but they do work. Whether it's a Drillings, combo gun, SxS, or O/U, or even some coked up dream like this Triple Threat or Triple Crown, it's only a matter of how well the barrels are regulated at their selected range.

I'm not defending Chiappa in the least, as I think they're a company that's trying to capitalize on 1) standing on the shoulders of giants by producing cheap knock-offs, and 2) novelty by recreating novel firearm designs like this one. I'll admit, I've been tempted by a Rhino on a few occasions, and an 1887 Mare's Leg would be a hoot as a saddle gun, but I won't own one unless someday I find myself with more dollars than sense (tongue in cheek doesn't work via type).

Assuming the extra barrel weight doesn't throw off the balance and handling advantage typical of SxS and O/U shotguns, the Triple Crown might be an opportunity for waterfowlers to level the playing field to hold as many rounds as their autoloading and pump action counterparts. If the price were right on the Triple Threat, it'd be a 50% capacity upgrade over the SxS EAA/Baikal or Stoeger that many guys use for home defense.