The MATLAB Coder documentation has a section covering acclerating MATLAB code via MEX generation:
One page that's relevant to what you are seeing is:
It contains the statement:
Use MEX functions to accelerate MATLAB code only if user-generated code dominates the run time.
Avoid generating MEX functions if computationally intensive, built-in MATLAB functions dominate the run time. These functions are pre-compiled and optimized, so the MATLAB code is not accelerated significantly using a MEX function.
In MATLAB, sort is a built-in function that is hand-optimized and compiled. So the generated code likely won't be any faster and can be slower in some cases.
