The default Flexible experience is that the user selects an general game speed but the time controls don’t matter too much. If it were exact, it’d starve one of the time control options.
See Revisiting Automatch Time Settings: Data-Backed Proposal for New Automatch Settings on OGS for discussion and analysis regarding those selections.
That said, it’s my plan to do some followup analysis after a bit and course correct if appropriate.