"MinMax Running Resettable" just following the input when using variable step size in simulink

I'm running a simulink (Simscape) model and use a MinMax Running Resettable to find the value of a continuous-time variable over simulation time. I see MinMax Running Resettable just follows the input (not doing a max() operation) with variable size step but works with fixed size steps. Is this expected (if yes, needs to be well documented)? Can I use this or another block with variable step size?

MATLAB Version 9.2 (R2017a) Simulink Version 8.9 (R2017a) Simscape Version 4.2 (R2017a) Simscape Electronics Version 2.11