Another factor (more closely related to the ABC story of the former senior Japanese submarine officer believing Australia to be incapable of fabricating Soryu hulls), many Japanese tend to look at Australia through a filter of "we find this thing hard to do, we are better than Australians, therefore Australians will find this thing impossible to do".
What I have written may sound judgemental or even racist but comes from experience of working in R&D for a Japanese automotive manufacturer and that is literally the bias we encountered all the time. We would have to repeat tests over and over again, produce multiple drafts of reports, have a cast of thousands (well a dozen or so engineers and managers) witness tests and even then still have our findings doubted. Often we would not be believed until the test was witnessed by a Japanese engineer or the same results were reproduced by a Japanese team. Simply they believed themselves superior to Australians therefore they automatically doubted anything we produced that they themselves had not, if what we found differed from their experience or suggested a problem with something they had designed the standard position was that we were wrong and must have stuffed it up.
Australians have risen to the highest levels globally in engineering, manufacturing, science, design, medicine, I could go on, but the stereo type of lazy, dumb, drunk and racist makes it very common for many cultures to look down at us in a way that when we used to do it to them was rightfully seen as racist and now they do it to us still is.
The irony in this is that ASC is among the world best at welding and fabrication. This was the case during the Collins build and continues to this day in the Collins maintenance, including cutting and re-welding the hulls, as well as the excellent job done on the AWDs. ASC fixes the problems from other builders, hull sections from Sweden, blocks from BAE, pipe segments from contractors, as well as completing their own work to worlds best practice. Its not just me saying this, it has been certified by Lloyds of London, as well as noted by each and every professional review of either the submarine or destroyer project. Senior surveyors from ABS, experienced shipbuilders and engineers from BIW, Navantia, Kockums, EB, USN etc. ASC are among the best when it comes to bashing steel.
It is quite common for ASCs abilities to be disregarded or even denied, but then again many (including unfortunately many ignorant Australians) like to deride the abilities and achievements of Australians in engineering, science, medicine, manufacturing, agriculture, mining, to name a few. The dumb, dunk and racist stereotype is believed rather than the reality of the majority being hard working and capable. Structural problems resulting from a small population, on a very large land mass, geographically separated from the rest of the world, exacerbated by political opportunism, inconsistency, lack of vision and sometimes, stupidity, as well as the greed of a small but very powerful minority, hold the county back and often prevent us from reaping the rewards due the talent and effort of so many.
It is hardly surprising that a retired senior naval officer who without a doubt is a patriot and rightfully proud of his countries achievements may believe that Australia is incapable of fabricating submarine hulls when Japan find it so difficult to do it. Then again the previous defence minister stood up in parliament and publicly canned ASC, which was rich coming from a corporate lawyer who probably doesn't know one end of a screw driver from another, so how can you blame the average member of public, let alone a member of an overseas navy for having doubts.