Discrepancy in API document and response for Sheet Object

I noticed in the Sheet Object API document, https://smartsheet.redoc.ly/tag/sheetsObjects#section/Sheet-Object, the field is "proofs" object, while in the API response for the same for "Get Sheet" API, the field is a "proof" object.

There is a difference in singular and plurality,

Is this a discrepancy? Can you please help me clarify this.