I can't pretend to speak for Clare... but I think the idea is to give
the students a sense of accomplishment within a short time frame.
Writing a game from scratch can be a daunting proposition - something
near impossible to have a bunch of budding programmers do in a short
time.
I remember starting Pygame like that :-)
However, having students start with a game skeleton, and
letting them use their creativity to "fill in the blank" could result
in something both doable in a reasonable time and fun to do.
I think Pygame is simple enough that if Clare is familiar with it, she could easily teach them. However, the benefits of a game shell are numerous. I don't know of such a thing though--game skeletons tend to be specific to the game and not particularly adaptable to various genres. My brother would like to learn programming in a similar way, though, if possible... Is there one? I'm interested as well.
As a teacher at heart, I fully support Clare's idea and wish I could help in a timely fashion.
As do I.
André