In 7.1, people complained about two scenarios that might've resulted in this change. One was that if you're like me and set your AP speed to 90 in a 55, enter a restricted zone, then jerk the wheel to take control back, the car will rocket back from 60 to 90. The other is sometimes AP mis-reads Route 110 as speed limit 110mph and start going faster.
I presume this is a safety feature to never allow AP to increase the setpoint but allow it to decrease it. I wish it were selectable as a preference though.
I definitely agree that the previous situation needed to be changed...any steering input that cancelled autosteer suddenly rocketed up to the TACC set point! But why not do the obvious thing (joke directed towards head pitchman), and just make the TACC set point also limited to 5mph over when previously in autopilot.
The chosen change is fine for fixing the problem, but now requires the driver to reset the target speed exiting every small town, etc. less "auto"