Dispersal had several functions. As you surmised, easier to launch 100 bombers from 25 bases than 4. It also increased the targeting problem requiring far more missiles or bombers. With the increase in targets it increased the chances that all weapons (1 or 2) on a target might fail or miss. It gave a visible display of readiness.
Equally it had the disadvantage of longer lines of logistics though RAF resources were planned to maintain near and far dispersals. Initially we had our own Anson which could carry a full V-bomber crew. Also organic Hastings and Varsities with any available Transport Command aircraft pressed in as well.
It also moved most of the bombers outside the ring of steel, the Bloodhound sites surrounding the bases from Finningley to Honington. The Thor bases at the time were also inside that ring.