According to the technical report [1], they used character portraits from Getchu [2] for training data. A cursory glance shows that the overwhelming majority of the characters are female. As a result, the characters the tool generates are likely to appear female to our eyes.
After the code is open sourced, perhaps someone should try to create make.boys.moe using character portraits from otome games [3].
[1]: 12.8 MB PDF, http://make.girls.moe/technical_report.pdf
[2]: example from report (possibly NSFW?), http://www.getchu.com/soft.phtml?id=933144
[3]: games with a female protagonist and many male characters, https://vndb.org/g542
The last line of the comment was aiming to bring my point across (which seems to have failed) - people do not need to label themselves as anything in order to be who they are.
Please re-read my post with a little more of a light heart - the sooner we all stop defining ourselves (and others) so seriously as members of tribes old and new, the sooner we can all speak to each other on a level playing field.
Shit, we're over capacity, this is against fire safety regulations!