I completely disagree.
The pressure of the system sealed up simply *must* allow the gasses to comingle and the evidence shows it does. If large water molecules will flow through, gassy air will as well. That air carries with it sound from the exhaust.
The unwelded center ovals through which the pipes are joined are there for support of the unwelded connections- not to seal any distinct chambers. We are then left with one unsealed chamber, pipes with holes in them, and a non-sealed pipe connecting them to the welds outside the open unit. The two cylinder banks are open to another. The gasses must mix and they do. They mix enough that the black soot coats the inside of the metal casing evenly across the two unsealed chambers. If the two chambers were distinct, the patterns would be unique. Welds would exist between them. There are none. Air flows. It joins the air from one bank to the other and rids us of the loppy sound we'd get otherwise.
It's a crossover. Whether we think it *looks* like enough of one or not doesn't matter. We don't know how much of an opening is needed, but we do know that one exists. It's really as simple as that, not only to my eye, but to my sense of logic.
Edit:
Provided research for support.
Besides, every V8 without a cross between the two banks will sound like lop sided ass. It's amplified in a dragster, but this is the extreme example of the resonance that joining the two banks is meant to allay.
Here's a solid link on how they work and why V8 exhausts are designed to be joined. And here's a pic also of a ~1" connection in an H pipe. Doesn't take a lot to balance the sound.
Here is a video of a straight pipe without any x over or H pipe. Note the loppies. This is what you hear bc the cylinder banks fire at times other than one another, send that sound straight out only their own side, and your ears are left looking for balance. You can almost visualize the cylinders moving up and down with the separate sounds:
https://www.youtube.com/watch?v=b6-zwK5th-4 Check at 1:37 for the same car with X Over pipes. It reveals a lot.
Also, they make clear that the smaller the openings between the two banks, the more low end performance will be gained. This is very good insight along with the small openings shown in the pics of the OE unit. We can infer that the smaller openings move less air and provide more back pressure which increases low end torque. This off-the-line grunt exactly what sells BMWs- especially a giant SAV, so the smaller openings make good 0-60 sense.
It also meshes well many folks experience of losing lower end grunt but seeing a happier rev up top. It never did make sense to me before, but now that I see it and pair the E53 experience with that of my E39 540, it's very clear.