Yes, less time is needed for domestic flights (SJC DFW), but since this is an international flight (SJC DFW CUN), they will need to check your passport and any other travel documents that may be needed at point of initial departure. AND they will be classifying this to be an international flight, not meeting their cut off times may be problematic if there are any issues along the way.

What's your risk tolerance level? Would any form of travel interruption be acceptable, especially since you could reduce the odds by meeting their stated minimums?