For me, if it has more than 5 pin stacks it takes twice as long or longer for me to manipulate.
You can load a 5 stack with security pins, whatever and I am confident it'll be open within 5 minutes. 7 if I am having a bad day.
The minute it has 6 or 7 sets, I lose my ability and feel reduced to luck more than skill. And then it takes 15 minutes.
What confounds you?