It has nothing to do with how long the flight is listed in the timetable, it's based on flight distance -- 900 miles to be precise.
On flights ranging from 900-1,399 miles, enjoy a full chef-curated meal service. Find breakfast and lunch items on flights departing from 5 AM to 1:30 PM, dinner for departures from 4 PM to 8 PM and a hearty selection of snacks at most times in between.
ORD-ATL is 606 miles and DTW-MCO is 958 miles. Note the specific meal time requirements. Also, where are you pulling this 10 minute number from?? I looked in the timetables and there's generally about a 30 minute difference in flight duration (around 2 hours for ORD-ATL and 2.5 hours for DTW-MCO).