Well One presumes that is module with the control/command deck in it.
Many modern submarines have rafted modules that then go into the hull. So they may not actually be building anything structural, but like the interior fitout modules. Think kinda like the joinery in a kitchen.
Heres one from an Astute.
View attachment 50038
They may even use aluminium for some of this.
Again, this would be Austal USA, building them in the USA, with US workers, US management, US government oversight etc. Logically looking at AUKUS this would make it easier for in the future to Austal Australia to send Australian workers over there, or have US workers come to Australia.
With the LCS program wrapping up some people might be looking for work and be interested in relocating, even if only temporarily.
Austal seems to have found its niche in the US, with the flight II of the spearhead class, which looks like taking more of the medical role within the US Navy and away from super big hospital ships like Comfort and Mercy. Which have always been problematic, and then in covid proved to be very difficult to use, even in cities like new york with highly developed port facilities.
The cats can move very quickly into positions at high speed with minimal crew. You can then fly your doctors and nurses in nearby and move them onto the ships. Being a cat, they are stable platforms, and for medical purposes, usually located in well sheltered bays etc. The Cat design allows a small ship to have a big interior volume and very few ladders/stairs which is obviously ideal for a medical ship. They are big enough to land large helicopters directly onto the ships, but do not need to embark them permanently.
Being much smaller and more numerous, with shallow drafts, you can locate them much closer to where they are needed and at more austre ports or bays.
But even then, that program isn't limitless. Austal picking up some other work would make a lot of sense for them.
Like most military items, ships and submarines aren't just made out of one material anymore. Welding plate steel to a hull and welding aluminium are different arts.