@theilikepie : Or maybe they're just written for fun?
Like think of it more on twitter art tag (like the fairly famous let's meet at witches gathering / 魔女集会で会いましょう ) or gamejam, where one base concept is the starting point and people build from there regardless of skills or execution (though admittedly the people who show up usually have some level of skills)
In this case you need to start with a 'villainess', a fiance, the threat of breaking relation with the fiance and that by the end the 'villainess' has to be happy.
So a person might see this, think 'it'd be cool if X happens' and try to fit it in somehow (yuri with heroine, the affair was fake, she's ok with breaking off engagement, keikaku doori, etc)
Yeah the quality is going to be all over the place, but the point of these isn't about finding the 'best of them' (that's a subjective thing anyway), but rather to enjoy the variety of it.