If I understand it correctly, the auto-clutching mechanism tries to anticipate your intention. So if you press hard on the throttle in the 1st gear and then ease off, it thinks that you are about to brake. It disengages the clutch in anticipation of the braking. However, you continue to press on the gas, and it engages the clutch again. The cycle continues....
This is indeed a problem, but something which can be easily overcome by any of the three fixes (press on it, ease of it, shift up to 2nd). And I am glad it is not just a Z4 thing. And for the record, SMG, even the Z4 version, is the best thing since sliced bread.
2011 528 Black/Black ZPP ZP2 BMW Apps
2005 330Ci SparkGraphite/Gray Retired ZHP, Step, Nav, Xenon, Heated Seats, PDC
2007 X3 3.0si AlpiWhite/Tobacco ED Retired Step, ZSP, ZPP, ZCW, PDC, Nav, Xenon, Privacy Glass, Servotronic, Cargo Net
2002 745Li Slate Green Metallic/Beige Retired; Perfect baby-hauler
2006 525 TiAg/Black Retired; nice but not an E39
2004 3.0 Z4 Black/Black/Black SMG Retired but not forgotten...
2003 525iA TiAg/Gray Retired; Long live the King of all Bimmers, the E39