Im glad you brought this up. I've been meaning to do the same. I notice this behavior with highway on-ramps. I will get a rate of acceleration I'm comfortable with and hold that.. The Speed and RPM's seem to be climbing at a synchronized rate and then on 3rd gear or 4th.. Maybe both. Thats when the RPM side just hovers around 3k RPMish but the Speed is still rising so I assume if the clutch was slipping like it would in a traditional manual tranny my speed would be dropping off.
Like you, this behavior concerns me of clutches slipping and burning up. If I let up on the gas it seems to do this less and will just shift into 5th/6th.
I've never smelled burnt clutch so it must be by design. (at least that's what convinces me).
FWIW, My clutches were completely replaced a few months back due to a TSB involving leaking seals. Prior to getting the clutches replaced. My shifts were all over the place, never could find the right gear and made a horrible noise at some RPM's. After the new clutches, it's like a completely brand new car. No shifting problems except for just this strange slipping sensation.
I definitely hope it's supposed to do that and that I'm not looking at replacing clutches at 36k miles.
I firmly believe though that the DCT tranny will never see 100k miles without some major repairs. If it turns out the average life of the DCT transmission exceeds 100k. I'll be mighty impressed.
2012 FF Ti HB Platinum White Tricoat, Built 12/11, 401A + Parking Technology Package and MFT w/NAV at 3.5.1