Only because its derivative.

Asking students to do something a la Christo isn't the same as asking them to rethink space and landscape as Christo did in Running Fence ( which bounded space without enclosing it.)

Its not the girl who is lacking artistic imagination, but her instructor. And considering that she sounds like the only student to enclose a large public space, she may be the only one who "got" what Christo was up to; including her instructor.

There are a lot of things declared "not art" which are.

Dante
Dante

Off to rewatch Matthew Barney's "The Order"