Given the right strain, it might take longer and or yield more. The Roots will consume a majority of the container in a 5 gal bucket. 3 gal might not be enough water for them the whole life of the plant without potential issues. With Autos there is the Autoflowering genes that will also determine when they start to flower. It is a combination of Roots nutes,, environment and genes on Autofloweing strains that determine when they start to flower. With larger root space in Hydro and Coco the Autoflowering strain triggers itself to start to flower later than in a smaller container. It typically stays in veg longer, which leads to longer Flowering times. I am not sure why Organic Soil grows do NOT follow this, as MOST properly grown Organic plants tend to finish more on time in larger pots. If you listen to some of the Kis Podcasts, I believe it is like what Jeff Lowenfell was talking about in an episode. Organic Soil seems to "UNLOCK" the virtual KEYS that help trigger Flowering sooner. Most likely the PK triggers get unlocked faster? More research had to be done to determine optimal conditions for earlier flower production in Autoflower strains. The sooner the plant "unlocks" these virtual doors, the sooner they hit Flower. With large pots of Coco or Water, the plants tend to keep vegging longer. They are not triggered as fast as plants that are in good Organic Soil in the same size container.
For example, if you put a Strawberry Nuggets in a 5 gal bucket of good Organic soil and it is properly taken care of, it will finish sooner than both the Coco and Hydro plants. What is the difference? The root system on a plant in a 5 gal bucket of Coco or DWC will be MUCH larger than any soil grown plant. So I believe the plants in Coco and Hydro keep their energy focused on making more ROOTS longer and not on budding in larger pots. Once the plant opens the "doors" to start flowering, the plants energy is the focused on budding instead of rooting and vegging.
If you keep a seedling in a Solo cup of Coco, it will start to preflower sooner than in a 5 gal bucket of Coco. The roots get bounded up and the trigger is bud sooner, as a way of self preservation. I believe that organic soil plants are triggered differently because of their metabolism is different as a result of how they eat. Slow and steady vs fast and Furious eating plays a role in how long the stay in Veg mode. I would love to study how we as Auto growers can manipulate the cycle length more in our favor. Peace, slowandeasy