Just my o-pinion (pun intended)
I just dealt with this same issue on my build. I found that once I got it (middle drawing) into my head, it was very easy to understand.
Study and understand the middle picture. It clearly shows a 0.0* relationship pinion to transmission.
What I found confusing was that I kept seeing transmission as a Horizontal line. Forget Horizontal, its just the "drawn" engine/transmission center line.
If you lift the rear of your car by the rear axle/wheels till the engine/transmission are level, then it makes it easier to understand pinion down/up (IMO).