Yes, development spends a lot of time trying to figure out where a set will take the metagame, but by that point the design is already handed off
In addition to these commonalities, there's another major overlapping presence in both of these sets: Shocklands
On the front, we've got Vanille, who doesn't do anything more than a Grapple with the PastGrapple with the Past, and a fairly potent card advantage engine in Fang
While black specializes in trading life for cards, blue dominates the stack with countermagic and traditional draw spells
Even if you are all in on the poison counter plan, Ixhel gives you a way to play your opponent's spells so long as they have three or more counters on them
When spray painting a magic card its impossible to avoid overspray which will leave remnants of black paint on the cards side edges