SharePoint ULS logs HTTP 304 Not Modified responses with errors - by design?

We've noticed a correlation between HTTP 304 responses to requests for SharePoint Style Library assets and ULS error-like messages in the same correlation such as:

Event ID ab1a9

Failed to get document content data. System.ComponentModel.Win32Exception (0x80004005): Cannot complete this function at Microsoft.SharePoint.SPSqlClient.GetDocumentContentRow(Int32 rowOrd, Object ospFileStmMgr, SPDocumentBindRequest& dbreq, SPDocumentBindResults& dbres)

Event ID abq2i

Could not get DocumentContent row: 0x80004005.

Event ID aiv4w

Spent 0 ms to bind -1 byte file stream

Event ID aise3

Failure when fetching document. 0x80070012

Does anyone know if it's by design? Is this correlation real or accidental?