I think the point is the order of the purchases, which is very important. In your end deck, you have trade routes, a quarry, ironworks, and silvers in your deck. We probably all agree these are important to the deck you want to build (well not the silvers, that sounds bad, but semi-necessary?).
So what is important is when we purchase it. The reason ironworks doesn't work so well at the start is, at best, it will be a gainer for quarry and provide you with another dollar, even possibly getting you to highway purchase. While this case sounds good, the likelihood isn't all that great. Quarry opening ensures early highway purchase on T3/T4. You were very fortunate to hit highway still, while also having the 1 highway, and 1 ironworks line up afterwards.
While the silver is necessary with the ironworks, as getting to $5 is pretty important, with quarry, it is not as essential for the counter reason. Thus, the extra trashing from trade route is very much wanted at the start.
Moreless, this deck does not want treasures, so much so that your first gold is surely a mistake. With that in mind, quarry is infinitely better than silver in this case, which makes the quarry/trade route opening a lot better.