The purpose of any polysyndeton is for rhetorical effect.

It is not. Polysyndeton is defined as instances in which several conjunctions are repeated, as in the sentence "he ran and jumped and laughed and played." Polysyndeton especially refers to instances in which these conjunctions could be replaced with commas, and make for an easier reading experience.

The phrase "deeper harder faster" does not include any conjunctions, and is then not an example of polysyndeton.

Writers use polysyndeton to create a sense of rhythm, emphasize each item in a list, or add a sense of urgency or intensity to their writing. It can also build up a feeling of accumulation or give the impression of endlessness to a situation or description.

We have ships and men and money and stores...

He ran and jumped and laughed for joy.