I'm thinking that's a 'typical' sample that the lab ran into on this barrel. At 500x, I'd think those inclusions have been effectively managed. Since it came from the barrel, that sample has been drawn down to a tiny percentage of the raw starting material.

New inclusions might be introduced, but that picture does not appear to be at the surface or near a weld. Chances are those inclusions were larger, but may have been reduced and dispersed by the extensive forging.