Software engineer job is not different from any other and I can't see any reason why it SHOULD be.
The combination of all of these factors makes software a different sort of beast than a lot of other work. Now, as I said, that doesn't mean that you can't still attack it with brute force and obtain results, but software is actually one of the realms where that is one of the least effective strategies.
Your statement about design vs implementation shows that you're clearly outside of your knowledge space when talking about other disciplines. Depending on bridge span, length, and construction method, the man hours required for design can be much more than those required for construction.
Software is not really all that different from any other type of work. It even shares the trait that people that are part of the software sector think that their sector is somehow inherently different.
I haven't said, nor do I mean to imply, that my dad is better than your dad, err, I mean, that software development is somehow on a higher plane or superior to other work. However, there is something that sets software apart from most other work in that it is almost entirely design work, even "construction" is design work. (Of course, there is often something that sets most genres of work apart from other genres too, every industry has its unique aspects.) A particular engineering task might require more man-hours in design than in construction but that is an edge case, and the ratio is unlikely to be higher than an order of magnitude, the norms still apply. And again, software sees a rather larger range of scale than almost any other industry. The difference in, say, the amount of data handled by a given piece of software can range from a single byte (or even a single bit) up to petabytes or higher (the LHC processes zettabytes of data per year). That's 21 orders of magnitude. The difference between the smallest features in a microchip and the longest superhighways on Earth is only 15 magnitudes, and those are considered to be hugely different industries.
The main point I wanted to get at though was that due to the primacy of design individual talent can often have an outsized impact on overall product quality or capability. You certainly see that in many other disciplines but not necessarily on the same scale. Because, again, it's not terribly rare to have a situation where a piece of software developed by a single developer is just generally better than one developed by a team working at a multi-billion dollar mega-corp. That's the equivalent of some guy building a Mach 10 plane in his garage that runs on solar power. You tend not to see extremes on such magnitudes outside of software.
Indeed, it's even a driving force in the industry, as the idea of being able to build some new or better product from nothing and scale up to a billion dollar company in a matter of years starting from only one or two founders is rather common in software and shockingly uncommon outside of it.
1. Spans N orders of magnitude in scale which is M orders of magnitude more than X sector.
2. A single individual can put out superb products while some teams put out mediocre products.
3. The possibility exists for companies to be created with J founders and reach a valuation of K in L years.
Sorry, but none of these are unique to software. They're just the same arguments for anything else with different values for the variables.
Again, your sector is not unique. Last time we thought software was a unique sector lead to the great "paradigm shift" (as Greenspan called it, I believe) of 2000. You might know it better as the dot-com bubble.
That this makes two industries "equivalent" is an even more far-fetched claim than InclinedPlane's.