When I made that shot I used 3 programs. Blender for 3D, Adobe Animate for 2D, and Adobe After Effect to bring both together, I also created the lighting for the 2D animation within After Effects. The reason I used adobe animate instead of grease pencil in blender is because I didn't know how to use grease pencil at the time and I still don't. However I do feel like I wouldn't have gotten the effect I was desiring if I used grease pencil. As I want the 2D Anim to interact with the lighting in a certain way to give the vibe I was looking for. I don't want it to just look like a 2D image placed in a 3D scene with a light to dark fade as it walks past the light. you know what I mean. have a nice day mate :D