I think the thrilling part is that it's a somewhat atomic concept that can somewhat convincingly be proven to not exist in the training data. While poetry is more impressive if it's as original it's harder to show that it's not just stitched together from the training data.
I just asked GPT-4 to come up with more such "provably original idioms":
"""
Here are a few more examples of idioms with meaningful and provable atomic originality:
"The kite has touched the stars" - This phrase could mean that someone has achieved a seemingly impossible goal or reached a level of success that was thought to be unattainable.
"The paint has mingled on the canvas" - This idiom might convey the idea that once certain decisions are made or actions taken, the resulting outcome can't be easily separated or undone, similar to colors of paint that have blended together on a canvas.
"The clock has chimed in reverse" - This expression could be used to describe a situation where something unexpected and unusual has occurred, akin to the unlikely event of a clock chiming in reverse order.
"The flower has danced in the wind" - This phrase could signify that someone or something has gracefully and nimbly adapted to changing circumstances, just as a flower might sway and move in response to the wind.
"""
