I’m not sure about that, as I have the exact same “black screen”, no matter, between what WPs I travel, or when going through TPs and the same holds on BNet. I just tested it before I wrote the post, you quoted.
Nevertheless, even if there is technically a loading screen, it is short enough nowadays, such that it doesn’t influence the game on any half way modern PC.
But that does not fix the problem. The timing is still off.
I never realized it and both in SP and on BNet I didn’t notice it at all, when I tried it a few minutes ago.