pdflatex -draftmode much slower compared to draft option passed to graphicx

pdflatex -draftmode much slower compared to draft option passed to graphicx

I found that passing -draftmode to pdflatex does not change the compile
time of my document (~10 minutes) at all, while passing draft to graphicx
reduces it to about 1 minute. From the documentation I thought that
-draftmode should have the same effect when the long compile time is
caused by a lot of figures (mine are mostly in pdf format).
Since -draftmode doesn't yield a pdf I cannot check if the graphics are
included or not.
edit:
From man pdflatex:
-draftmode
Sets \pdfdraftmode so pdfTeX doesn't write a PDF and
doesn't read any included images, thus speeding up execution.
"doesn't read any included images" sounds to me quite similar to what
draft does with graphicx.
$ pdflatex --version
pdfTeX 3.1415926-2.4-1.40.13 (TeX Live 2012/Debian)
kpathsea version 6.1.0
Copyright 2012 Peter Breitenlohner (eTeX)/Han The Thanh (pdfTeX).
There is NO warranty. Redistribution of this software is
covered by the terms of both the pdfTeX copyright and
the Lesser GNU General Public License.
For more information about these matters, see the file
named COPYING and the pdfTeX source.
Primary author of pdfTeX: Peter Breitenlohner (eTeX)/Han The Thanh (pdfTeX).
Compiled with libpng 1.2.46; using libpng 1.2.46
Compiled with zlib 1.2.3.4; using zlib 1.2.3.4
Compiled with poppler version 0.18.4