It is a time-zone issue. The flight is scheduled to arrive at 12:50pm LOCAL time (meaning at 12:50pm Mexico City time).
It is easy to get confused because parts of arizona do not follow daylight savings time and Mexico adjusts for DST using different dates than the US.
Considering reduced flight loads and no particular issues, your time in MEX passport control and customs should be quite brief - 30 minutes or less. I have traveled through there in peak holiday season with multiple flights with full loads being processed at the same time and the wait has not been more than 40 minutes.
I think if you plan with the expectation of leaving the airport 1 hour after arrival you should be just fine.