Minimum Transfer Time

Hi,

I’m trying to plan out an ordered, sizable hub in DTW where the minimum transfer time is 1hr 30min. However, it shows on the scheduling page that there are valid connections with only 55min of transfer time. Why is this? Are some flights exempt from this longer transfer time of 1hr and 30min? I appreciate any help!

Flights done by the same aircraft.
That is to say, PAX don’t have to deboard the aircraft

That makes sense, thanks!