I think that they have been manufactured for the old style firebox and for some reason only now come to market. I have been in correspondence with Kamado Joe about it (asking if I was installing it correctly) and they sent me pictures showing how it should be placed in the AMP fireboxes (same as I have in my 2018 Big Joe) with the same issue. They said that the X rack now has to be used in the low position with the deflector plates on top of it. Here are the picture that they sent to me. I have to admit to being disappointed, the basket is £125 here in the UK (around $165) so not a cheap accessory. The quality and function is top notch (although this issue does also mean that you loose about an inch of depth in the firebox which may be an concern for a very long cook). This morning I picked out the basket, having yesterday done a 5 hour cook with perfectly stable temperature, shook it a couple of times over a flowerbed to clean off the coals and the Joe was good to go. I think the concept is brilliant and worth the outlay, I just wish it fit properly!
@Pigfqr I would think 6-9 hours at those temps should be in the ballpark, I really tried to stay low on that cook because usually I'm up closer to 300 and my stall is pretty much a non event at that heat, but I wanted to experiment a bit and try a really long cook. I held 220 for about 12 hours when I started running out of lump (one of the butts was just leaving the stall at that point) and then it was another 1.5 to 2 hours in the oven at 275. My porketta took a bit longer than the BBQ one because it ended up being thicker when it was all rolled up. I would say both ended up being equally moist. I think next time I want to get separate pans under each one because I bet an au jus made of the porketta drippings would be pretty great. I need to find a smaller size than the half steamer foil pans I've been using.