I think it's mostly ease of handling. Shorter barrels weigh less and are much easier to use in tight spaces. In modern rifles they're less accurate, but not at the ranges infantry use them. With the shotgun i imagine choke is at least as important as barrel length.
In the us, i think so, at least on paper. Afaik this gun is being marketted as a last-ditch point defense for ukrainian soliders under attack by explosive drones.