It's 2 different kind of "fillets"
"Fillet" is also used for the roundings formerd by the soldifiie-ing solder.
This depends for a lagre part on the stencil thickness and the amount of solder, and KiCad has no knowledge of these parameters.
In technical drawings the term "fillet" is used for rounded corners. I just had a look at the Footprint Editor in Kicad, and there rounded pads are apparently defined still differently. ("Corner size" as a persentage of the pad widht).
But it does not matter much.
The more important thing is that I dropped a message yesterday on the KiCad forum, and apparently a pull request for a fix is available on github.
https://github.com/KiCad/kicad-source-mirror/commit/68e6308066a3bd0a4fcbf6aae8c4869d075aae3eOn my PC the Python code for the wizard is in:
/usr/share/kicad/scripting/plugins/qfn_wizard.py
I'm a total noob with Python, but I was curious, so I modified the python script by hand (guided by the patch suggestion), then compiled it with info I found on:
https://askubuntu.com/questions/324871/how-to-compile-a-python-fileand I copied the output to:
/usr/share/kicad/scripting/plugins/__pycache__/qfn_wizard.cpython-37.pyc
Then I started KiCad, and "fillet" has indeed been renamed to "offset", and pad length seems correct and offset moves the pas more to the outside.
It was pretty easy to do, even for a total Python Noob such as me. I do not know however how long it takes before the change is available in the official KiCad release.
I am very impressed by the quick response of the KiCad developers. I've seen it before that small fixes like this get fixed within a few days.
Some notes:
I always get confused by Python 2 and Python 3, and I may have compiled it wrongly...
Those scripts are in a readonly directory, which makes it a bit harder to modify. (Rightly so).
Make backups of the original files before changing anything. I like to prepend the original file with a date in ISO6801 format:
> cp qfn_wizard.py 2019-04-17_qfn_wizard.py
The official Footprints for QFN packages have rounded corners. These are also generated from scripts, but they use a different script then the Footprint Wizards.