re #2: looking at the source code I don't see this behavior. Perhaps in a version from the past? Anyway, please advise or point me to a jira...

In src/mongo/db/db.cpp I see:

    void _initAndListen(int listenPort ) {
        ...
        dur::startup(); // <- this i believe preallocs journal files
        ...
        listen(listenPort); // after journal prealloc i think

p.s. this blog post is a very interesting article overall i think, without commenting on all the specifics...