What is the Concept of MATLAB Function Polynomial Interpolation?
It is basically an approach choice.
Inside the math is identical.

Usually, when doing Least Squares curve fitting, you're not looking for the Polynomial coefficients but a scaled version of them.
For instance, if you try to estimate Range, Velocity and Acceleration from Range Measurements using LS you need to scale the Polynomial Coefficients according to the dynamic model.

By the way, most of the times, you can do the LS estimation using $ {\left( {H}^{T} H \right)}^{-1} {H}^{T} $ which would be faster than pinv.
The only case it won't work is when $ \left( {H}^{T} H \right) $ isn't invertible (Rarely occurs in real world measurements).