I think one parallel could be the Invasion of France in 1940 by Germany. They attacked on all fronts, along the whole border at Netherlands, Belgium, Luxembourg, and France, but the main thrust which served to reach the sea and slice the Allied armies in two was started out at Luxembourg. They did not attack just through the Ardennes while sit in cover on the rest of the front, not even along the Maginot line.

Back to the date of mid-April. The Battle of Bakhmut was still raging on and over a month more. Ukraine needed all the manpower - which wasn't spent on preparing the brigades of their summer campaign (9+3) - to throw them against the Wagner. I think it was major distraction from the plans of starting the offensive in the spring.