Not for the same recipe. With shared capacity, its monthly output is divided by the number of enabled recipes in that building. Independent recipes each retain their own capacity.
Your own example: a recipe rated at 6,000 L/month gets 3,000 L with two recipes sharing capacity. A 5,000 L target then needs two buildings; with independent capacity it needs one.
On PC, check the building XML: sharedThroughputCapacity="false" means independent; true or an omitted flag uses shared capacity. If unsure, enable only the recipe you want to plan and enter 1. Count enabled recipes, not the full recipe list.