Does predict function work in parallel when predicting k-nearest neighbour?

I have a k-nearest neighbour classifier which I have trained with fitcknn. I am wondering, when predicting labels on the model using predicit does it work in parallel? I have tested using predict in a for loop and parfor loop. The simple for loop performs a bit faster which makes me think there is some optimisation and built in parallelisation that the predict function is taking advantage of. However, the documentation makes no reference to this, and I thought MATLAB always runs in a single thread unless specifically using a parallel pool?