> Basically, link testing use the main connection.
> Background downloads may use more, but after all
> headers are processed (ie. for updates, you will not
> notice any parallel processing, because you only
> have "not modified" replies, and no data)

Note that this feature allows to have reliable file types on the local
filesystem, even with ambiguous redirects.

You can, however, disable it, and obtain the 3.3X series behaviour, by using
the following option:

-%N0