File it under "stuff that matters".
A lot of arguments for open source are based on things which people outside the project could in principle accomplish, but in practice seldom do. So it's reassuring at least that an experienced developer can build the two most popular browsers from scratch. It means the arguments aren't hollow. I've seen closed source projects that were purchased by companies, only to find out that getting them to build on any computer but the one it was developed on is a serious engineering challenge.
That the process of building these browsers from scratch is somewhat arcane will come as no surprise to any experienced developer. But that it's not so arcane that it's impractical to figure out is good news.