yeah...it was hard figuring out exactly what this meant when we reviewed it. The actual scoring criteria is that "the response identifies the purpose of the program." So that's what we want students to aim for. The decision rules give this exception that the response can earn the point if they describe the function instead of the purpose.
Our take on this is that for some programs its function might be so tightly coupled to its purpose that they're trying to cut some slack to students who start out describing a purpose but slip into describing its function. For example think about something like Uber (an app that it's safe to say no CSP student is going to make for the Create PT).... "The purpose is to request a ride on your phone by using GPS to know your location so a driver can come pick you up."
Seems like a plausible student response that melds the purpose and function together.
It's all kind of gray territory. Hope that's helpful.