I think it's silly to talk about the A/B plot as if it's not something Discovery does. Discovery does this all the time. Some examples:
Season 1: All the Klingon shit in the early part of the season basically happened on a parallel track to Discovery. Choose Your Pain, Lethe, and Si Vis Pacem, Para Bellum all had pretty conventional A/B plot structures as well.
Season 2: New Eden was A/B (Typical planetside/shipside split of the crew). Point of Light had four different plots. Light and Shadows and Through the Valleyof Shadows were both A/B stories as well.
Season 3: The spectacular Forget Me Not was a clear A/B story. Also, Sa'Kul and the season finale jumped back and forth between the ship and Saru & company trying to calm "the child" down.
It's also worth noting that even when episodes don't have A/B structures, they still pepper in scenes which are clearly meant just to give secondary cast members something to do that week. A lot of the banter between Stamets, Tilly, and Reno in spore drive or engineering for example. Or in the third season the "no nowhere" story of Adira and Grey later in the arc.