Confused by the different handling of debconf questions when using dpkg-reconfigure

[Emmanuel Kasper <emmanuel.kasper@openforce.com>]

Hello
I notice that when I install postfix, it asks me then a couple of
questions using debconf, and create then a default configuration file
using my answers.

If I call now `dpkg-reconfigure postfix` debconf asks me the same
questions PLUS a bunch of new questions which I did not have in the
first in the first place.  I find it confusing.

Is i a bug, a feature, am I missing something ?

Manu