You have not given a link to the PIR documentation or posted your code.
The problem must be a differnece between the way the Arduino handled the stay on delay and the way the PIR handles the stay on delay.
Maybe your sketch was turning the light on when motion was first detected and turning it off one minute after motion was last detected i.e. it could keep the light on for ages as the timer is reset every time motion is detected.
On the other hand the PIR might start a timer when motion is detected but not try to reset it until the end of the period. So light comes on when motion is first detected and will go off after a minute unless moton is still being detected at the time when the minute has elapsed.
I am just guessing but it has to be something along these line. Playing with the PIR and a multimeter or reading the PIR documentation and comparing it with how the sketch works should give the answer.