I understand your background and understanding of how automatic and manual transmissions work, but an automatic and dual-clutch are not the same thing by any stretch of the imagination. Yes, you can control the shifting of an automatic with the help of electrical controls and goodies, but, to my understanding, the primary component in them is the torque converter, which uses hydraulic pressure to allow the transmission to 'slip' while changing gears. Yes, it produces a crazy amount of heat, but it doesn't work the same as a dual-clutch.
A dual-clutch transmission is exactly that: Two clutches, just like the dry clutch used in your manual transmission. One clutch - consisting of multiple friction plates - is connected to the odd gears, 1-3-5-7 and another is connected to the even gears 2-4-6. As you shift, it disengages the engaged clutch and engages the other clutch, while shifting the mechanical components similarly to how you shift your manual transmission.
Why I suggest this is the reason for more frequent oil changes is the debris that will be released from the clutch pad material as it shifts hard between each gear, not from excessive heat.
My $0.02.
Nah, your dual clutch is doing the same thing the "old fashioned" automatic is doing: it applies and disengages all those clutch packs on every shift. Toss in that it also has engagement "bands" that are also friction material lined and there's"boat loads" of friction material contamination running around in a "traditional" automatic. Have a look at an "old" TH400 cutaway:
Everywhere you see those brown/beige colored discs is a clutch with friction material. Lots and lots of them in there. And that doens't even take into account the bands which also have friction material that contaminates the fluid. As well, newer auto's with lock up convetors have even more friction material running int he trans fluid.
The torque convertor is just a viscous coupling that multiplies the torque from the engine and keys into the trans body to run the hydraulic pump (which supplies fluid pressure for clutch pack operations). If you've ever seen the "two fan" demonstration/example, you'll understand how the torque convertor works. in a nutshell; the engine spins one fan and the air it drives turns the other fan. Torque convertor does the same thing, it just uses fluid instead of air like a fan would. Split open a torque convertor and you are actually going to see turbines, which are a type of fan:
To be technical, it's actually termed "rotor" and "stator". One is attached to the torque convertor body and is spun by the engine, the other is connected to the transmission input shaft and is spun by the fluid driven by the engine side. That's it in a nutshell, except modern TC have clutches in them to lock up the convertor for better MPG in steady state highway type operations.
You can sit at idle with the brakes on because of that viscous coupling, but as soon as it's moving, the clutch packs and bands do all the heavy work. The clutch packs are what engages/disengages every time the car shifts, not the torque convertor. The clutches ride in the fluid, but they also use fluid pressure to schedule the shifting. It's all hydraulic in "traditional" auto's. Electronic auto's still use the fluid to shift, it's just through electric solenoids instead of just springs, balls, valving and passages/ports.
All "old fashioned" automatics contaminate the oil with the clutch friction material. It's why they have a massive filter in the bottom of the pan. Overheat them and they absolutely pollute the oil with friction material, along with glazing the clutches and bands. They still run out to 100k before needing a change. But overheat the fluid
ONCE and it's
DONE. Change it or expect transmission damage shortly thereafter. Or at the very least, significantly reduced transmission life expectancy. The sucky thing about transmission fluid and overheating is that most vehicles don't have a temp guage or even an idiot light. You can fry your trans fluid and not even know it. That's why my F-150 has an otpion on the electronic cluster to swap the boost guage for a transmission temp gauge. the temp guage is up all the time on mine. I could care less how much boost it's making as I have no control over that other than my right foot and it's going to "bypass" at a predetermined pressure anyways. Nope, I'd rather know if that trans fluid is toasted or not...
Nah, I'm sticking with "heat" being the biggest concern for fluid life and why the interval seems so low to me.
But, I've also been wrong before so it wouldnt be the first time....LOL!