Official position: do both.
Practical position: if you only do Java, you can skip pic.loadPixels(); because an image, unlike PGraphics, has always the pixels loaded.
Caveat: I understand that in Android mode, and perhaps in other modes, it is necessary.
Conclusion: unless you are very sure to use only the Java mode, better safe than sorry and so both! The cost is minim and can save headaches for people trying to use your code.
Side note: arrayCopy can do part of the job...