There should be a lower limit where Garmin connect should display standstill and not 40minutes/km.
Look at this http://connect.garmin.com/modern/activity/639161884
Now I can barely tell the difference from my warm up pace 6min/km to my fastest intervall 3min/km since the scale of the session goes from 40minutes/km to 00 minutes/km.
Now that can't take that much coding to get right.
It does even work in the Connect app on Iphone.