Not really...
1. Black Label may be dealing with darker themes often times true, but the stories themselves don't end out like bad ends. The Dark Multiverse is like the bad end multiverse, there's a difference between dark stories and bad endings. At least, I'm assuming that'll be a possible difference between the two, although I'm unsure of that.
2. Black Label seems to be more about original story ideas, whereas Tales from the Dark Multiverse is more reimagining or retelling classic storylines and taking them in new dark directions. While both may handle darker stories, they do fundamentally deliver different sets of stories - original ideas vs reimaginings and retellings. It's an important distinction to separate the two.
Sorry to quote you twice, but you edited your response so I had more I wanted to respond to.