You need to understand that the side entrances are used with two follower boards, as follows (see The Barefoot Beekeeper for full instructions).
Initially, the followers are placed either side of an introduced swarm or nucleus, with entrance holes also placed centrally, so the colony is held within the central third of the hive body. This means that they have a manageable volume within which to build their first combs, and I have found that this greatly increases the likelihood of these combs being built to follow the starter strips.
As comb building progresses, ONLY ONE follower is moved, two or three bars ahead of where the bees are building, so as to allow them to expand their colony unhindered. The space on the empty side of the non-moving follower is for use in making splits for increase or swarm prevention, if required.
The colony continues its expansion in one direction, initially placing stores above the brood, and the excess in combs beyond the brood area. As the colony contracts at the end of the season, the cluster forms close to the stored honey, and during the winter, they eat their way through their stores, comb by comb, moving away from the entrance. At no time is there any need to 'shuffle' combs. (Exceptionally, they may leave a comb of honey between the brood nest and the non-moving follower, which can be re-positioned at the far end if it is felt necessary.)
If - as is usually the case - there are empty combs either end of the colony as it approaches winter, they can be removed for melting (or stored for replacement in the same colony in the spring, if required). This enables the beekeeper easily to reduce the volume of the hive in winter, so the bees can more easily retain their heat.
Another major advantage of movable followers is that they enable the beekeeper to do a quick inspection of both ends of the colony at any time, with virtually no disturbance to the bees. You can check both stores and brood nest in a matter of seconds, without moving a single top bar, simply by sliding a follower away. Most times I do this, the bees barely notice. If I need to look a little deeper into the brood nest, for example, if I need to check for eggs or brood, then I can do so by moving only one or two top bars.
If you hold the colony against one end of the hive with a single follower - or use no followers at all - you cannot ever inspect the brood nest without moving nearly every bar in the hive!
As I said, the empty space beyond the non-moving follower can be used for making splits and for swarm control, as I provide it with another entrance on the opposite side of the hive to the main entrance.